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	$48.65	7.652%	$52.3727	$52.37	$52.35	$52.40
Purchase #2	$169.80	12.403%	$190.8603	$190.86	$190.85	$190.90
Purchase #3	$229.74	9.145%	$250.7497	$250.75	$250.75	$250.70
Purchase #4	$146.27	7.535%	$157.2914	$157.29	$157.30	$157.30
Purchase #5	$49.59	8.697%	$53.9028	$53.90	$53.90	$53.90
Purchase #6	$155.27	7.206%	$166.4588	$166.46	$166.45	$166.50
Purchase #7	$125.96	8.267%	$136.3731	$136.37	$136.35	$136.40
7 purchase totals =	$925.28		$1,008.0088	$1,008.00	$1,007.95	$1,008.10