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	$227.71	11.482%	$253.8557	$253.86	$253.85	$253.90
Purchase #2	$152.68	3.802%	$158.4849	$158.48	$158.50	$158.50
Purchase #3	$216.50	12.402%	$243.3503	$243.35	$243.35	$243.40
Purchase #4	$11.71	9.713%	$12.8474	$12.85	$12.85	$12.80
Purchase #5	$229.74	10.245%	$253.2769	$253.28	$253.30	$253.30
Purchase #6	$211.90	6.389%	$225.4383	$225.44	$225.45	$225.40
Purchase #7	$220.29	8.278%	$238.5256	$238.53	$238.55	$238.50
7 purchase totals =	$1,270.53		$1,385.7791	$1,385.79	$1,385.85	$1,385.80