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	$22.29	12.679%	$25.1161	$25.12	$25.10	$25.10
Purchase #2	$130.45	7.376%	$140.072	$140.07	$140.05	$140.10
Purchase #3	$230.55	5.574%	$243.4009	$243.40	$243.40	$243.40
Purchase #4	$151.94	12.180%	$170.4463	$170.45	$170.45	$170.40
Purchase #5	$141.50	3.782%	$146.8515	$146.85	$146.85	$146.90
Purchase #6	$189.75	3.581%	$196.5449	$196.54	$196.55	$196.50
Purchase #7	$86.71	10.639%	$95.9351	$95.94	$95.95	$95.90
7 purchase totals =	$953.19		$1,018.3668	$1,018.37	$1,018.35	$1,018.30