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	$153.65	4.155%	$160.0342	$160.03	$160.05	$160.00
Purchase #2	$169.96	6.528%	$181.055	$181.06	$181.05	$181.10
Purchase #3	$19.30	13.432%	$21.8924	$21.89	$21.90	$21.90
Purchase #4	$75.78	13.359%	$85.9035	$85.90	$85.90	$85.90
Purchase #5	$49.40	12.332%	$55.492	$55.49	$55.50	$55.50
Purchase #6	$49.71	12.196%	$55.7726	$55.77	$55.75	$55.80
Purchase #7	$22.99	5.373%	$24.2253	$24.23	$24.25	$24.20
7 purchase totals =	$540.79		$584.3750	$584.37	$584.40	$584.40