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	$59.89	8.624%	$65.0549	$65.05	$65.05	$65.10
Purchase #2	$42.83	13.423%	$48.5791	$48.58	$48.60	$48.60
Purchase #3	$63.76	13.419%	$72.316	$72.32	$72.30	$72.30
Purchase #4	$216.65	12.785%	$244.3487	$244.35	$244.35	$244.30
Purchase #5	$18.29	12.204%	$20.5221	$20.52	$20.50	$20.50
Purchase #6	$202.76	11.102%	$225.2704	$225.27	$225.25	$225.30
Purchase #7	$37.91	7.413%	$40.7203	$40.72	$40.70	$40.70
7 purchase totals =	$642.09		$716.8115	$716.81	$716.75	$716.80