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	$104.28	11.468%	$116.2388	$116.24	$116.25	$116.20
Purchase #2	$30.29	11.168%	$33.6728	$33.67	$33.65	$33.70
Purchase #3	$9.28	9.617%	$10.1725	$10.17	$10.15	$10.20
Purchase #4	$249.81	12.637%	$281.3785	$281.38	$281.40	$281.40
Purchase #5	$250.76	6.830%	$267.8869	$267.89	$267.90	$267.90
Purchase #6	$72.49	4.143%	$75.4933	$75.49	$75.50	$75.50
Purchase #7	$66.92	6.858%	$71.5094	$71.51	$71.50	$71.50
7 purchase totals =	$783.83		$856.3522	$856.35	$856.35	$856.40