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	$41.84	9.607%	$45.8596	$45.86	$45.85	$45.90
Purchase #2	$198.48	13.629%	$225.5308	$225.53	$225.55	$225.50
Purchase #3	$13.77	5.733%	$14.5594	$14.56	$14.55	$14.60
Purchase #4	$110.81	4.698%	$116.0159	$116.02	$116.00	$116.00
Purchase #5	$101.92	3.572%	$105.5606	$105.56	$105.55	$105.60
Purchase #6	$129.95	13.552%	$147.5608	$147.56	$147.55	$147.60
Purchase #7	$140.42	3.800%	$145.756	$145.76	$145.75	$145.80
7 purchase totals =	$737.19		$800.8431	$800.85	$800.80	$801.00