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	$75.45	3.439%	$78.0447	$78.04	$78.05	$78.00
Purchase #2	$41.66	4.344%	$43.4697	$43.47	$43.45	$43.50
Purchase #3	$164.52	9.635%	$180.3715	$180.37	$180.35	$180.40
Purchase #4	$144.91	4.525%	$151.4672	$151.47	$151.45	$151.50
Purchase #5	$159.67	13.274%	$180.8646	$180.86	$180.85	$180.90
Purchase #6	$102.65	12.680%	$115.666	$115.67	$115.65	$115.70
Purchase #7	$242.45	11.145%	$269.4711	$269.47	$269.45	$269.50
7 purchase totals =	$931.31		$1,019.3548	$1,019.35	$1,019.25	$1,019.50