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	$59.80	3.713%	$62.0204	$62.02	$62.00	$62.00
Purchase #2	$69.62	4.525%	$72.7703	$72.77	$72.75	$72.80
Purchase #3	$146.91	7.784%	$158.3455	$158.35	$158.35	$158.30
Purchase #4	$7.58	13.343%	$8.5914	$8.59	$8.60	$8.60
Purchase #5	$54.51	4.635%	$57.0365	$57.04	$57.05	$57.00
Purchase #6	$228.76	11.134%	$254.2301	$254.23	$254.25	$254.20
Purchase #7	$170.88	3.512%	$176.8813	$176.88	$176.90	$176.90
7 purchase totals =	$738.06		$789.8755	$789.88	$789.90	$789.80