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	$215.76	4.501%	$225.4714	$225.47	$225.45	$225.50
Purchase #2	$72.88	11.283%	$81.1031	$81.10	$81.10	$81.10
Purchase #3	$40.77	10.825%	$45.1834	$45.18	$45.20	$45.20
Purchase #4	$106.86	13.175%	$120.9388	$120.94	$120.95	$120.90
Purchase #5	$16.45	12.158%	$18.45	$18.45	$18.45	$18.50
Purchase #6	$111.33	8.269%	$120.5359	$120.54	$120.55	$120.50
Purchase #7	$90.55	4.749%	$94.8502	$94.85	$94.85	$94.90
7 purchase totals =	$654.60		$706.5328	$706.53	$706.55	$706.60