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	$149.96	13.643%	$170.419	$170.42	$170.40	$170.40
Purchase #2	$143.43	9.705%	$157.3499	$157.35	$157.35	$157.30
Purchase #3	$43.82	6.245%	$46.5566	$46.56	$46.55	$46.60
Purchase #4	$157.34	11.426%	$175.3177	$175.32	$175.30	$175.30
Purchase #5	$196.34	6.397%	$208.8999	$208.90	$208.90	$208.90
Purchase #6	$221.57	10.719%	$245.3201	$245.32	$245.30	$245.30
Purchase #7	$109.35	9.244%	$119.4583	$119.46	$119.45	$119.50
7 purchase totals =	$1,021.81		$1,123.3215	$1,123.33	$1,123.25	$1,123.30