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	$140.51	7.508%	$151.0595	$151.06	$151.05	$151.10
Purchase #2	$221.63	13.625%	$251.8271	$251.83	$251.85	$251.80
Purchase #3	$239.26	4.793%	$250.7277	$250.73	$250.75	$250.70
Purchase #4	$19.40	4.824%	$20.3359	$20.34	$20.35	$20.30
Purchase #5	$152.95	4.428%	$159.7226	$159.72	$159.70	$159.70
Purchase #6	$198.93	11.647%	$222.0994	$222.10	$222.10	$222.10
Purchase #7	$246.32	4.176%	$256.6063	$256.61	$256.60	$256.60
7 purchase totals =	$1,219.00		$1,312.3785	$1,312.39	$1,312.40	$1,312.30