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	$219.82	9.419%	$240.5248	$240.52	$240.50	$240.50
Purchase #2	$232.82	4.534%	$243.3761	$243.38	$243.40	$243.40
Purchase #3	$57.51	3.471%	$59.5062	$59.51	$59.50	$59.50
Purchase #4	$249.40	11.536%	$278.1708	$278.17	$278.15	$278.20
Purchase #5	$205.71	6.291%	$218.6512	$218.65	$218.65	$218.70
Purchase #6	$243.31	13.471%	$276.0863	$276.09	$276.10	$276.10
Purchase #7	$155.26	13.261%	$175.849	$175.85	$175.85	$175.80
7 purchase totals =	$1,363.83		$1,492.1644	$1,492.17	$1,492.15	$1,492.20