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	$250.67	10.707%	$277.5092	$277.51	$277.50	$277.50
Purchase #2	$233.79	12.404%	$262.7893	$262.79	$262.80	$262.80
Purchase #3	$114.29	3.230%	$117.9816	$117.98	$118.00	$118.00
Purchase #4	$136.44	10.309%	$150.5056	$150.51	$150.50	$150.50
Purchase #5	$159.81	3.590%	$165.5472	$165.55	$165.55	$165.50
Purchase #6	$21.95	10.694%	$24.2973	$24.30	$24.30	$24.30
Purchase #7	$16.58	11.640%	$18.5099	$18.51	$18.50	$18.50
7 purchase totals =	$933.53		$1,017.1401	$1,017.15	$1,017.15	$1,017.10