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	$173.37	5.774%	$183.3804	$183.38	$183.40	$183.40
Purchase #2	$98.83	12.535%	$111.2183	$111.22	$111.20	$111.20
Purchase #3	$46.69	9.733%	$51.2343	$51.23	$51.25	$51.20
Purchase #4	$147.34	9.575%	$161.4478	$161.45	$161.45	$161.40
Purchase #5	$159.74	3.594%	$165.4811	$165.48	$165.50	$165.50
Purchase #6	$137.38	10.769%	$152.1745	$152.17	$152.15	$152.20
Purchase #7	$183.98	13.546%	$208.9019	$208.90	$208.90	$208.90
7 purchase totals =	$947.33		$1,033.8383	$1,033.83	$1,033.85	$1,033.80