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	$45.93	13.708%	$52.2261	$52.23	$52.25	$52.20
Purchase #2	$234.43	12.227%	$263.0938	$263.09	$263.10	$263.10
Purchase #3	$21.65	5.495%	$22.8397	$22.84	$22.85	$22.80
Purchase #4	$203.89	5.735%	$215.5831	$215.58	$215.60	$215.60
Purchase #5	$151.30	10.294%	$166.8748	$166.87	$166.85	$166.90
Purchase #6	$169.68	12.738%	$191.2938	$191.29	$191.30	$191.30
Purchase #7	$80.53	13.721%	$91.5795	$91.58	$91.60	$91.60
7 purchase totals =	$907.41		$1,003.4908	$1,003.48	$1,003.55	$1,003.50