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	$193.53	8.576%	$210.1271	$210.13	$210.15	$210.10
Purchase #2	$158.80	9.447%	$173.8018	$173.80	$173.80	$173.80
Purchase #3	$200.83	10.307%	$221.5295	$221.53	$221.55	$221.50
Purchase #4	$75.27	9.428%	$82.3665	$82.37	$82.35	$82.40
Purchase #5	$211.30	5.344%	$222.5919	$222.59	$222.60	$222.60
Purchase #6	$130.30	8.672%	$141.5996	$141.60	$141.60	$141.60
Purchase #7	$198.91	6.474%	$211.7874	$211.79	$211.80	$211.80
7 purchase totals =	$1,168.94		$1,263.8038	$1,263.81	$1,263.85	$1,263.80