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	$122.62	7.556%	$131.8852	$131.89	$131.90	$131.90
Purchase #2	$151.83	13.344%	$172.0902	$172.09	$172.10	$172.10
Purchase #3	$195.43	9.439%	$213.8766	$213.88	$213.90	$213.90
Purchase #4	$39.58	13.222%	$44.8133	$44.81	$44.80	$44.80
Purchase #5	$78.52	10.204%	$86.5322	$86.53	$86.55	$86.50
Purchase #6	$83.80	3.470%	$86.7079	$86.71	$86.70	$86.70
Purchase #7	$82.34	6.571%	$87.7506	$87.75	$87.75	$87.80
7 purchase totals =	$754.12		$823.6560	$823.66	$823.70	$823.70