Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$142.95	5.237%	$150.4363	$150.44	$150.45	$150.40
Purchase #2	$65.65	4.284%	$68.4624	$68.46	$68.45	$68.50
Purchase #3	$226.94	4.417%	$236.9639	$236.96	$236.95	$237.00
Purchase #4	$178.25	6.755%	$190.2908	$190.29	$190.30	$190.30
Purchase #5	$114.25	7.707%	$123.0552	$123.06	$123.05	$123.10
Purchase #6	$201.83	12.663%	$227.3877	$227.39	$227.40	$227.40
Purchase #7	$204.99	10.210%	$225.9195	$225.92	$225.90	$225.90
7 purchase totals =	$1,134.86		$1,222.5158	$1,222.52	$1,222.50	$1,222.60