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	$120.89	3.735%	$125.4052	$125.41	$125.40	$125.40
Purchase #2	$175.32	4.341%	$182.9306	$182.93	$182.95	$182.90
Purchase #3	$143.36	3.708%	$148.6758	$148.68	$148.70	$148.70
Purchase #4	$66.72	6.333%	$70.9454	$70.95	$70.95	$70.90
Purchase #5	$106.52	7.859%	$114.8914	$114.89	$114.90	$114.90
Purchase #6	$78.66	13.749%	$89.475	$89.48	$89.50	$89.50
Purchase #7	$146.93	3.768%	$152.4663	$152.47	$152.45	$152.50
7 purchase totals =	$838.40		$884.7897	$884.81	$884.85	$884.80