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	$144.59	4.178%	$150.631	$150.63	$150.65	$150.60
Purchase #2	$52.54	13.856%	$59.8199	$59.82	$59.80	$59.80
Purchase #3	$236.77	11.330%	$263.596	$263.60	$263.60	$263.60
Purchase #4	$83.72	11.604%	$93.4349	$93.43	$93.45	$93.40
Purchase #5	$33.79	5.864%	$35.7714	$35.77	$35.75	$35.80
Purchase #6	$48.50	4.344%	$50.6068	$50.61	$50.60	$50.60
Purchase #7	$17.85	12.866%	$20.1466	$20.15	$20.15	$20.10
7 purchase totals =	$617.76		$674.0066	$674.01	$674.00	$673.90