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	$177.51	9.431%	$194.251	$194.25	$194.25	$194.30
Purchase #2	$249.34	13.300%	$282.5022	$282.50	$282.50	$282.50
Purchase #3	$250.48	11.200%	$278.5338	$278.53	$278.55	$278.50
Purchase #4	$57.39	8.325%	$62.1677	$62.17	$62.15	$62.20
Purchase #5	$175.83	10.628%	$194.5172	$194.52	$194.50	$194.50
Purchase #6	$194.78	8.643%	$211.6148	$211.61	$211.60	$211.60
Purchase #7	$243.25	13.265%	$275.5171	$275.52	$275.50	$275.50
7 purchase totals =	$1,348.58		$1,499.1038	$1,499.10	$1,499.05	$1,499.10