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	$59.48	5.192%	$62.5682	$62.57	$62.55	$62.60
Purchase #2	$182.25	11.868%	$203.8794	$203.88	$203.90	$203.90
Purchase #3	$8.59	4.605%	$8.9856	$8.99	$9.00	$9.00
Purchase #4	$215.88	3.105%	$222.5831	$222.58	$222.60	$222.60
Purchase #5	$131.88	11.128%	$146.5556	$146.56	$146.55	$146.60
Purchase #6	$85.95	4.388%	$89.7215	$89.72	$89.70	$89.70
Purchase #7	$35.31	6.759%	$37.6966	$37.70	$37.70	$37.70
7 purchase totals =	$719.34		$771.9900	$772.00	$772.00	$772.10