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	$111.64	13.658%	$126.8878	$126.89	$126.90	$126.90
Purchase #2	$156.53	9.766%	$171.8167	$171.82	$171.80	$171.80
Purchase #3	$156.39	5.533%	$165.0431	$165.04	$165.05	$165.00
Purchase #4	$227.40	10.129%	$250.4333	$250.43	$250.45	$250.40
Purchase #5	$220.54	10.573%	$243.8577	$243.86	$243.85	$243.90
Purchase #6	$222.40	13.283%	$251.9414	$251.94	$251.95	$251.90
Purchase #7	$185.74	8.411%	$201.3626	$201.36	$201.35	$201.40
7 purchase totals =	$1,280.64		$1,411.3426	$1,411.34	$1,411.35	$1,411.30