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	$66.28	8.245%	$71.7448	$71.74	$71.75	$71.70
Purchase #2	$243.89	13.593%	$277.042	$277.04	$277.05	$277.00
Purchase #3	$76.55	6.225%	$81.3152	$81.32	$81.30	$81.30
Purchase #4	$82.37	8.348%	$89.2462	$89.25	$89.25	$89.20
Purchase #5	$159.53	8.369%	$172.8811	$172.88	$172.90	$172.90
Purchase #6	$118.34	6.827%	$126.4191	$126.42	$126.40	$126.40
Purchase #7	$75.64	12.494%	$85.0905	$85.09	$85.10	$85.10
7 purchase totals =	$822.60		$903.7389	$903.74	$903.75	$903.60