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	$188.41	9.572%	$206.4446	$206.44	$206.45	$206.40
Purchase #2	$59.27	3.252%	$61.1975	$61.20	$61.20	$61.20
Purchase #3	$54.42	6.438%	$57.9236	$57.92	$57.90	$57.90
Purchase #4	$151.81	9.620%	$166.4141	$166.41	$166.40	$166.40
Purchase #5	$49.61	7.260%	$53.2117	$53.21	$53.20	$53.20
Purchase #6	$68.50	7.813%	$73.8519	$73.85	$73.85	$73.90
Purchase #7	$92.70	8.388%	$100.4757	$100.48	$100.50	$100.50
7 purchase totals =	$664.72		$719.5191	$719.51	$719.50	$719.50