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	$48.93	3.403%	$50.5951	$50.60	$50.60	$50.60
Purchase #2	$59.42	5.635%	$62.7683	$62.77	$62.75	$62.80
Purchase #3	$144.93	4.224%	$151.0518	$151.05	$151.05	$151.10
Purchase #4	$191.55	4.582%	$200.3268	$200.33	$200.35	$200.30
Purchase #5	$57.25	12.162%	$64.2127	$64.21	$64.20	$64.20
Purchase #6	$168.74	4.391%	$176.1494	$176.15	$176.15	$176.10
Purchase #7	$145.64	3.190%	$150.2859	$150.29	$150.30	$150.30
7 purchase totals =	$816.46		$855.3900	$855.40	$855.40	$855.40