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	$120.71	9.173%	$131.7827	$131.78	$131.80	$131.80
Purchase #2	$171.45	8.131%	$185.3906	$185.39	$185.40	$185.40
Purchase #3	$118.56	8.701%	$128.8759	$128.88	$128.90	$128.90
Purchase #4	$62.45	3.867%	$64.8649	$64.86	$64.85	$64.90
Purchase #5	$220.78	11.731%	$246.6797	$246.68	$246.70	$246.70
Purchase #6	$232.48	4.473%	$242.8788	$242.88	$242.90	$242.90
Purchase #7	$52.96	4.643%	$55.4189	$55.42	$55.40	$55.40
7 purchase totals =	$979.39		$1,055.8915	$1,055.89	$1,055.95	$1,056.00