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	$222.72	6.730%	$237.7091	$237.71	$237.70	$237.70
Purchase #2	$64.25	9.667%	$70.461	$70.46	$70.45	$70.50
Purchase #3	$95.31	10.754%	$105.5596	$105.56	$105.55	$105.60
Purchase #4	$233.73	9.686%	$256.3691	$256.37	$256.35	$256.40
Purchase #5	$175.94	13.862%	$200.3288	$200.33	$200.35	$200.30
Purchase #6	$176.31	7.452%	$189.4486	$189.45	$189.45	$189.40
Purchase #7	$179.49	11.517%	$200.1619	$200.16	$200.15	$200.20
7 purchase totals =	$1,147.75		$1,260.0381	$1,260.04	$1,260.00	$1,260.10