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	$228.47	4.201%	$238.068	$238.07	$238.05	$238.10
Purchase #2	$49.44	5.579%	$52.1983	$52.20	$52.20	$52.20
Purchase #3	$140.66	6.315%	$149.5427	$149.54	$149.55	$149.50
Purchase #4	$211.42	7.178%	$226.5957	$226.60	$226.60	$226.60
Purchase #5	$48.96	11.220%	$54.4533	$54.45	$54.45	$54.50
Purchase #6	$143.82	4.387%	$150.1294	$150.13	$150.15	$150.10
Purchase #7	$105.96	4.665%	$110.903	$110.90	$110.90	$110.90
7 purchase totals =	$928.73		$981.8904	$981.89	$981.90	$981.90