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	$115.26	11.822%	$128.886	$128.89	$128.90	$128.90
Purchase #2	$105.33	5.437%	$111.0568	$111.06	$111.05	$111.10
Purchase #3	$26.67	7.505%	$28.6716	$28.67	$28.65	$28.70
Purchase #4	$72.82	3.472%	$75.3483	$75.35	$75.35	$75.30
Purchase #5	$221.86	13.739%	$252.3413	$252.34	$252.35	$252.30
Purchase #6	$35.92	7.244%	$38.522	$38.52	$38.50	$38.50
Purchase #7	$143.86	11.767%	$160.788	$160.79	$160.80	$160.80
7 purchase totals =	$721.72		$795.6140	$795.62	$795.60	$795.60