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	$103.53	7.254%	$111.0401	$111.04	$111.05	$111.00
Purchase #2	$130.90	4.112%	$136.2826	$136.28	$136.30	$136.30
Purchase #3	$21.31	7.319%	$22.8697	$22.87	$22.85	$22.90
Purchase #4	$123.57	7.299%	$132.5894	$132.59	$132.60	$132.60
Purchase #5	$53.89	9.439%	$58.9767	$58.98	$59.00	$59.00
Purchase #6	$60.62	3.650%	$62.8326	$62.83	$62.85	$62.80
Purchase #7	$127.89	8.303%	$138.5087	$138.51	$138.50	$138.50
7 purchase totals =	$621.71		$663.0998	$663.10	$663.15	$663.10