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	$57.25	13.343%	$64.8889	$64.89	$64.90	$64.90
Purchase #2	$129.27	6.103%	$137.1593	$137.16	$137.15	$137.20
Purchase #3	$57.35	7.719%	$61.7768	$61.78	$61.80	$61.80
Purchase #4	$100.83	4.795%	$105.6648	$105.66	$105.65	$105.70
Purchase #5	$174.33	11.871%	$195.0247	$195.02	$195.00	$195.00
Purchase #6	$95.31	3.565%	$98.7078	$98.71	$98.70	$98.70
Purchase #7	$243.32	13.262%	$275.5891	$275.59	$275.60	$275.60
7 purchase totals =	$857.66		$938.8114	$938.81	$938.80	$938.90