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	$103.83	13.355%	$117.6965	$117.70	$117.70	$117.70
Purchase #2	$108.82	11.192%	$120.9991	$121.00	$121.00	$121.00
Purchase #3	$35.85	4.542%	$37.4783	$37.48	$37.50	$37.50
Purchase #4	$231.85	7.619%	$249.5147	$249.51	$249.50	$249.50
Purchase #5	$33.25	13.570%	$37.762	$37.76	$37.75	$37.80
Purchase #6	$132.47	5.682%	$139.9969	$140.00	$140.00	$140.00
Purchase #7	$155.69	10.345%	$171.7961	$171.80	$171.80	$171.80
7 purchase totals =	$801.76		$875.2436	$875.25	$875.25	$875.30