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	$208.75	5.253%	$219.7156	$219.72	$219.70	$219.70
Purchase #2	$179.32	12.388%	$201.5342	$201.53	$201.55	$201.50
Purchase #3	$88.94	12.363%	$99.9357	$99.94	$99.95	$99.90
Purchase #4	$54.70	13.157%	$61.8969	$61.90	$61.90	$61.90
Purchase #5	$27.55	11.143%	$30.6199	$30.62	$30.60	$30.60
Purchase #6	$105.50	10.631%	$116.7157	$116.72	$116.70	$116.70
Purchase #7	$190.82	13.647%	$216.8612	$216.86	$216.85	$216.90
7 purchase totals =	$855.58		$947.2792	$947.29	$947.25	$947.20