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	$222.59	9.799%	$244.4016	$244.40	$244.40	$244.40
Purchase #2	$52.39	12.727%	$59.0577	$59.06	$59.05	$59.10
Purchase #3	$17.72	3.394%	$18.3214	$18.32	$18.30	$18.30
Purchase #4	$81.81	10.690%	$90.5555	$90.56	$90.55	$90.60
Purchase #5	$40.71	5.267%	$42.8542	$42.85	$42.85	$42.90
Purchase #6	$51.50	7.759%	$55.4959	$55.50	$55.50	$55.50
Purchase #7	$77.52	7.763%	$83.5379	$83.54	$83.55	$83.50
7 purchase totals =	$544.24		$594.2242	$594.23	$594.20	$594.30