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	$127.92	13.709%	$145.4566	$145.46	$145.45	$145.50
Purchase #2	$214.58	11.236%	$238.6902	$238.69	$238.70	$238.70
Purchase #3	$220.40	8.220%	$238.5169	$238.52	$238.50	$238.50
Purchase #4	$139.41	9.639%	$152.8477	$152.85	$152.85	$152.80
Purchase #5	$237.30	7.842%	$255.9091	$255.91	$255.90	$255.90
Purchase #6	$221.45	9.702%	$242.9351	$242.94	$242.95	$242.90
Purchase #7	$174.69	5.494%	$184.2875	$184.29	$184.30	$184.30
7 purchase totals =	$1,335.75		$1,458.6431	$1,458.66	$1,458.65	$1,458.60