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	$250.82	8.516%	$272.1798	$272.18	$272.20	$272.20
Purchase #2	$34.97	7.155%	$37.4721	$37.47	$37.45	$37.50
Purchase #3	$37.74	8.453%	$40.9302	$40.93	$40.95	$40.90
Purchase #4	$134.77	3.593%	$139.6123	$139.61	$139.60	$139.60
Purchase #5	$212.96	7.810%	$229.5922	$229.59	$229.60	$229.60
Purchase #6	$158.36	10.650%	$175.2253	$175.23	$175.25	$175.20
Purchase #7	$249.44	11.602%	$278.38	$278.38	$278.40	$278.40
7 purchase totals =	$1,079.06		$1,173.3919	$1,173.39	$1,173.45	$1,173.40