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	$45.29	6.240%	$48.1161	$48.12	$48.10	$48.10
Purchase #2	$141.44	7.436%	$151.9575	$151.96	$151.95	$152.00
Purchase #3	$44.37	12.544%	$49.9358	$49.94	$49.95	$49.90
Purchase #4	$246.33	10.378%	$271.8941	$271.89	$271.90	$271.90
Purchase #5	$30.93	8.578%	$33.5832	$33.58	$33.60	$33.60
Purchase #6	$195.51	9.717%	$214.5077	$214.51	$214.50	$214.50
Purchase #7	$150.50	5.288%	$158.4584	$158.46	$158.45	$158.50
7 purchase totals =	$854.37		$928.4528	$928.46	$928.45	$928.50