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	$64.58	13.462%	$73.2738	$73.27	$73.25	$73.30
Purchase #2	$89.66	6.764%	$95.7246	$95.72	$95.70	$95.70
Purchase #3	$40.80	11.409%	$45.4549	$45.45	$45.45	$45.50
Purchase #4	$116.95	6.786%	$124.8862	$124.89	$124.90	$124.90
Purchase #5	$52.96	3.848%	$54.9979	$55.00	$55.00	$55.00
Purchase #6	$64.25	7.427%	$69.0218	$69.02	$69.00	$69.00
Purchase #7	$132.96	8.382%	$144.1047	$144.10	$144.10	$144.10
7 purchase totals =	$562.16		$607.4639	$607.45	$607.40	$607.50