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	$180.51	7.706%	$194.4201	$194.42	$194.40	$194.40
Purchase #2	$173.92	8.188%	$188.1606	$188.16	$188.15	$188.20
Purchase #3	$82.73	8.609%	$89.8522	$89.85	$89.85	$89.90
Purchase #4	$114.62	13.158%	$129.7017	$129.70	$129.70	$129.70
Purchase #5	$247.75	10.271%	$273.1964	$273.20	$273.20	$273.20
Purchase #6	$84.26	6.622%	$89.8397	$89.84	$89.85	$89.80
Purchase #7	$62.52	13.115%	$70.7195	$70.72	$70.70	$70.70
7 purchase totals =	$946.31		$1,035.8902	$1,035.89	$1,035.85	$1,035.90