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	$140.43	8.174%	$151.9087	$151.91	$151.90	$151.90
Purchase #2	$214.52	13.672%	$243.8492	$243.85	$243.85	$243.80
Purchase #3	$55.83	7.222%	$59.862	$59.86	$59.85	$59.90
Purchase #4	$124.47	11.310%	$138.5476	$138.55	$138.55	$138.50
Purchase #5	$31.67	10.424%	$34.9713	$34.97	$34.95	$35.00
Purchase #6	$66.82	7.752%	$71.9999	$72.00	$72.00	$72.00
Purchase #7	$178.89	5.125%	$188.0581	$188.06	$188.05	$188.10
7 purchase totals =	$812.63		$889.1968	$889.20	$889.15	$889.20