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	$86.30	3.525%	$89.3421	$89.34	$89.35	$89.30
Purchase #2	$169.68	7.790%	$182.8981	$182.90	$182.90	$182.90
Purchase #3	$186.84	10.743%	$206.9122	$206.91	$206.90	$206.90
Purchase #4	$85.28	9.319%	$93.2272	$93.23	$93.25	$93.20
Purchase #5	$37.41	10.761%	$41.4357	$41.44	$41.45	$41.40
Purchase #6	$250.35	13.733%	$284.7306	$284.73	$284.75	$284.70
Purchase #7	$190.87	11.563%	$212.9403	$212.94	$212.95	$212.90
7 purchase totals =	$1,006.73		$1,111.4862	$1,111.49	$1,111.55	$1,111.30