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	$57.60	9.599%	$63.129	$63.13	$63.15	$63.10
Purchase #2	$151.27	5.144%	$159.0513	$159.05	$159.05	$159.10
Purchase #3	$245.28	6.707%	$261.7309	$261.73	$261.75	$261.70
Purchase #4	$40.50	13.309%	$45.8901	$45.89	$45.90	$45.90
Purchase #5	$66.78	7.672%	$71.9034	$71.90	$71.90	$71.90
Purchase #6	$36.37	12.576%	$40.9439	$40.94	$40.95	$40.90
Purchase #7	$105.26	11.697%	$117.5723	$117.57	$117.55	$117.60
7 purchase totals =	$703.06		$760.2209	$760.21	$760.25	$760.20