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	$74.88	5.159%	$78.7431	$78.74	$78.75	$78.70
Purchase #2	$230.83	9.594%	$252.9758	$252.98	$253.00	$253.00
Purchase #3	$121.86	3.733%	$126.409	$126.41	$126.40	$126.40
Purchase #4	$90.39	4.535%	$94.4892	$94.49	$94.50	$94.50
Purchase #5	$198.25	12.220%	$222.4762	$222.48	$222.50	$222.50
Purchase #6	$207.46	11.775%	$231.8884	$231.89	$231.90	$231.90
Purchase #7	$148.93	4.522%	$155.6646	$155.66	$155.65	$155.70
7 purchase totals =	$1,072.60		$1,162.6463	$1,162.65	$1,162.70	$1,162.70