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	$61.59	9.604%	$67.5051	$67.51	$67.50	$67.50
Purchase #2	$43.85	12.110%	$49.1602	$49.16	$49.15	$49.20
Purchase #3	$8.90	5.736%	$9.4105	$9.41	$9.40	$9.40
Purchase #4	$137.79	9.813%	$151.3113	$151.31	$151.30	$151.30
Purchase #5	$58.83	5.147%	$61.858	$61.86	$61.85	$61.90
Purchase #6	$85.64	10.787%	$94.878	$94.88	$94.90	$94.90
Purchase #7	$155.81	13.198%	$176.3738	$176.37	$176.35	$176.40
7 purchase totals =	$552.41		$610.4969	$610.50	$610.45	$610.60