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	$86.31	10.266%	$95.1706	$95.17	$95.15	$95.20
Purchase #2	$241.61	10.369%	$266.6625	$266.66	$266.65	$266.70
Purchase #3	$63.79	10.560%	$70.5262	$70.53	$70.55	$70.50
Purchase #4	$231.58	9.617%	$253.851	$253.85	$253.85	$253.90
Purchase #5	$48.63	11.639%	$54.29	$54.29	$54.30	$54.30
Purchase #6	$63.72	11.459%	$71.0217	$71.02	$71.00	$71.00
Purchase #7	$140.43	8.519%	$152.3932	$152.39	$152.40	$152.40
7 purchase totals =	$876.07		$963.9152	$963.91	$963.90	$964.00