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	$139.83	7.649%	$150.5256	$150.53	$150.55	$150.50
Purchase #2	$247.70	13.256%	$280.5351	$280.54	$280.55	$280.50
Purchase #3	$11.56	5.756%	$12.2254	$12.23	$12.25	$12.20
Purchase #4	$197.88	13.733%	$225.0549	$225.05	$225.05	$225.10
Purchase #5	$146.64	3.666%	$152.0158	$152.02	$152.00	$152.00
Purchase #6	$234.60	11.726%	$262.1092	$262.11	$262.10	$262.10
Purchase #7	$185.44	3.802%	$192.4904	$192.49	$192.50	$192.50
7 purchase totals =	$1,163.65		$1,274.9564	$1,274.97	$1,275.00	$1,274.90