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	$53.97	13.522%	$61.2678	$61.27	$61.25	$61.30
Purchase #2	$70.68	11.161%	$78.5686	$78.57	$78.55	$78.60
Purchase #3	$96.50	3.808%	$100.1747	$100.17	$100.15	$100.20
Purchase #4	$84.77	4.390%	$88.4914	$88.49	$88.50	$88.50
Purchase #5	$29.44	10.160%	$32.4311	$32.43	$32.45	$32.40
Purchase #6	$123.70	4.863%	$129.7155	$129.72	$129.70	$129.70
Purchase #7	$18.53	5.630%	$19.5732	$19.57	$19.55	$19.60
7 purchase totals =	$477.59		$510.2223	$510.22	$510.15	$510.30