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	$183.75	13.550%	$208.6481	$208.65	$208.65	$208.60
Purchase #2	$246.80	9.329%	$269.824	$269.82	$269.80	$269.80
Purchase #3	$243.63	4.633%	$254.9174	$254.92	$254.90	$254.90
Purchase #4	$12.57	10.650%	$13.9087	$13.91	$13.90	$13.90
Purchase #5	$100.78	8.351%	$109.1961	$109.20	$109.20	$109.20
Purchase #6	$70.60	10.811%	$78.2326	$78.23	$78.25	$78.20
Purchase #7	$153.37	5.327%	$161.54	$161.54	$161.55	$161.50
7 purchase totals =	$1,011.50		$1,096.2669	$1,096.27	$1,096.25	$1,096.10