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	$59.81	13.462%	$67.8616	$67.86	$67.85	$67.90
Purchase #2	$34.89	5.634%	$36.8557	$36.86	$36.85	$36.90
Purchase #3	$222.66	9.445%	$243.6902	$243.69	$243.70	$243.70
Purchase #4	$54.32	13.578%	$61.6956	$61.70	$61.70	$61.70
Purchase #5	$197.85	3.533%	$204.84	$204.84	$204.85	$204.80
Purchase #6	$80.87	10.640%	$89.4746	$89.47	$89.45	$89.50
Purchase #7	$194.39	9.660%	$213.1681	$213.17	$213.15	$213.20
7 purchase totals =	$844.79		$917.5858	$917.59	$917.55	$917.70