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	$85.60	3.545%	$88.6345	$88.63	$88.65	$88.60
Purchase #2	$99.81	8.386%	$108.1801	$108.18	$108.20	$108.20
Purchase #3	$209.85	5.487%	$221.3645	$221.36	$221.35	$221.40
Purchase #4	$160.82	7.320%	$172.592	$172.59	$172.60	$172.60
Purchase #5	$122.56	4.521%	$128.1009	$128.10	$128.10	$128.10
Purchase #6	$158.29	3.640%	$164.0518	$164.05	$164.05	$164.10
Purchase #7	$97.59	13.680%	$110.9403	$110.94	$110.95	$110.90
7 purchase totals =	$934.52		$993.8641	$993.85	$993.90	$993.90