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	$236.45	7.551%	$254.3043	$254.30	$254.30	$254.30
Purchase #2	$157.35	10.345%	$173.6279	$173.63	$173.65	$173.60
Purchase #3	$84.37	6.854%	$90.1527	$90.15	$90.15	$90.20
Purchase #4	$182.85	9.296%	$199.8477	$199.85	$199.85	$199.80
Purchase #5	$89.72	8.671%	$97.4996	$97.50	$97.50	$97.50
Purchase #6	$59.90	7.684%	$64.5027	$64.50	$64.50	$64.50
Purchase #7	$75.84	8.612%	$82.3713	$82.37	$82.35	$82.40
7 purchase totals =	$886.48		$962.3062	$962.30	$962.30	$962.30