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	$239.88	5.750%	$253.6731	$253.67	$253.65	$253.70
Purchase #2	$92.95	13.119%	$105.1441	$105.14	$105.15	$105.10
Purchase #3	$84.75	9.290%	$92.6233	$92.62	$92.60	$92.60
Purchase #4	$200.62	11.508%	$223.7073	$223.71	$223.70	$223.70
Purchase #5	$217.37	12.854%	$245.3107	$245.31	$245.30	$245.30
Purchase #6	$40.88	13.787%	$46.5161	$46.52	$46.50	$46.50
Purchase #7	$33.49	10.102%	$36.8732	$36.87	$36.85	$36.90
7 purchase totals =	$909.94		$1,003.8478	$1,003.84	$1,003.75	$1,003.80