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	$147.36	12.419%	$165.6606	$165.66	$165.65	$165.70
Purchase #2	$210.31	7.188%	$225.4271	$225.43	$225.45	$225.40
Purchase #3	$200.55	4.339%	$209.2519	$209.25	$209.25	$209.30
Purchase #4	$101.70	9.607%	$111.4703	$111.47	$111.45	$111.50
Purchase #5	$101.80	8.370%	$110.3207	$110.32	$110.30	$110.30
Purchase #6	$111.51	4.181%	$116.1722	$116.17	$116.15	$116.20
Purchase #7	$63.43	4.734%	$66.4328	$66.43	$66.45	$66.40
7 purchase totals =	$936.66		$1,004.7356	$1,004.73	$1,004.70	$1,004.80