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	$53.41	10.870%	$59.2157	$59.22	$59.20	$59.20
Purchase #2	$78.74	5.670%	$83.2046	$83.20	$83.20	$83.20
Purchase #3	$91.90	4.345%	$95.8931	$95.89	$95.90	$95.90
Purchase #4	$100.54	4.545%	$105.1095	$105.11	$105.10	$105.10
Purchase #5	$131.74	8.340%	$142.7271	$142.73	$142.75	$142.70
Purchase #6	$56.84	10.431%	$62.769	$62.77	$62.75	$62.80
Purchase #7	$132.92	13.698%	$151.1274	$151.13	$151.15	$151.10
7 purchase totals =	$646.09		$700.0464	$700.05	$700.05	$700.00