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	$111.67	8.419%	$121.0715	$121.07	$121.05	$121.10
Purchase #2	$109.90	12.338%	$123.4595	$123.46	$123.45	$123.50
Purchase #3	$34.91	4.733%	$36.5623	$36.56	$36.55	$36.60
Purchase #4	$42.72	6.647%	$45.5596	$45.56	$45.55	$45.60
Purchase #5	$127.44	7.137%	$136.5354	$136.54	$136.55	$136.50
Purchase #6	$220.80	13.508%	$250.6257	$250.63	$250.65	$250.60
Purchase #7	$31.56	4.385%	$32.9439	$32.94	$32.95	$32.90
7 purchase totals =	$679.00		$746.7579	$746.76	$746.75	$746.80