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	$88.71	4.738%	$92.9131	$92.91	$92.90	$92.90
Purchase #2	$177.54	9.674%	$194.7152	$194.72	$194.70	$194.70
Purchase #3	$40.49	11.760%	$45.2516	$45.25	$45.25	$45.30
Purchase #4	$148.76	13.235%	$168.4484	$168.45	$168.45	$168.40
Purchase #5	$140.90	8.451%	$152.8075	$152.81	$152.80	$152.80
Purchase #6	$37.99	8.726%	$41.305	$41.31	$41.30	$41.30
Purchase #7	$88.85	13.750%	$101.0669	$101.07	$101.05	$101.10
7 purchase totals =	$723.24		$796.5077	$796.52	$796.45	$796.50