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	$145.94	3.676%	$151.3048	$151.30	$151.30	$151.30
Purchase #2	$145.64	6.850%	$155.6163	$155.62	$155.60	$155.60
Purchase #3	$141.96	8.210%	$153.6149	$153.61	$153.60	$153.60
Purchase #4	$113.48	7.141%	$121.5836	$121.58	$121.60	$121.60
Purchase #5	$28.46	13.346%	$32.2583	$32.26	$32.25	$32.30
Purchase #6	$54.46	8.655%	$59.1735	$59.17	$59.15	$59.20
Purchase #7	$82.77	9.690%	$90.7904	$90.79	$90.80	$90.80
7 purchase totals =	$712.71		$764.3418	$764.33	$764.30	$764.40