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	$218.74	3.235%	$225.8162	$225.82	$225.80	$225.80
Purchase #2	$146.89	3.500%	$152.0312	$152.03	$152.05	$152.00
Purchase #3	$151.74	12.255%	$170.3357	$170.34	$170.35	$170.30
Purchase #4	$75.91	3.156%	$78.3057	$78.31	$78.30	$78.30
Purchase #5	$65.50	3.614%	$67.8672	$67.87	$67.85	$67.90
Purchase #6	$105.50	10.800%	$116.894	$116.89	$116.90	$116.90
Purchase #7	$8.95	3.625%	$9.2744	$9.27	$9.25	$9.30
7 purchase totals =	$773.23		$820.5244	$820.53	$820.50	$820.50