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	$193.47	7.733%	$208.431	$208.43	$208.45	$208.40
Purchase #2	$147.64	9.738%	$162.0172	$162.02	$162.00	$162.00
Purchase #3	$148.51	11.663%	$165.8307	$165.83	$165.85	$165.80
Purchase #4	$140.28	3.286%	$144.8896	$144.89	$144.90	$144.90
Purchase #5	$72.58	10.329%	$80.0768	$80.08	$80.10	$80.10
Purchase #6	$51.42	7.531%	$55.2924	$55.29	$55.30	$55.30
Purchase #7	$194.66	13.803%	$221.5289	$221.53	$221.55	$221.50
7 purchase totals =	$948.56		$1,038.0666	$1,038.07	$1,038.15	$1,038.00