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	$216.43	13.737%	$246.161	$246.16	$246.15	$246.20
Purchase #2	$22.59	6.640%	$24.09	$24.09	$24.10	$24.10
Purchase #3	$244.33	11.538%	$272.5208	$272.52	$272.50	$272.50
Purchase #4	$24.28	8.797%	$26.4159	$26.42	$26.40	$26.40
Purchase #5	$37.54	13.361%	$42.5557	$42.56	$42.55	$42.60
Purchase #6	$69.47	13.469%	$78.8269	$78.83	$78.85	$78.80
Purchase #7	$50.33	10.824%	$55.7777	$55.78	$55.80	$55.80
7 purchase totals =	$664.97		$746.3480	$746.36	$746.35	$746.40