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	$249.26	11.569%	$278.0969	$278.10	$278.10	$278.10
Purchase #2	$26.26	9.166%	$28.667	$28.67	$28.65	$28.70
Purchase #3	$215.70	3.629%	$223.5278	$223.53	$223.55	$223.50
Purchase #4	$102.96	8.581%	$111.795	$111.80	$111.80	$111.80
Purchase #5	$155.37	10.801%	$172.1515	$172.15	$172.15	$172.20
Purchase #6	$211.28	3.248%	$218.1424	$218.14	$218.15	$218.10
Purchase #7	$42.54	7.249%	$45.6237	$45.62	$45.60	$45.60
7 purchase totals =	$1,003.37		$1,078.0043	$1,078.01	$1,078.00	$1,078.00