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	$227.86	9.172%	$248.7593	$248.76	$248.75	$248.80
Purchase #2	$112.44	3.702%	$116.6025	$116.60	$116.60	$116.60
Purchase #3	$152.51	6.726%	$162.7678	$162.77	$162.75	$162.80
Purchase #4	$238.85	10.172%	$263.1458	$263.15	$263.15	$263.10
Purchase #5	$243.66	4.217%	$253.9351	$253.94	$253.95	$253.90
Purchase #6	$242.96	13.351%	$275.3976	$275.40	$275.40	$275.40
Purchase #7	$11.45	11.183%	$12.7305	$12.73	$12.75	$12.70
7 purchase totals =	$1,229.73		$1,333.3386	$1,333.35	$1,333.35	$1,333.30