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	$132.53	11.284%	$147.4847	$147.48	$147.50	$147.50
Purchase #2	$44.78	11.771%	$50.0511	$50.05	$50.05	$50.10
Purchase #3	$213.90	9.229%	$233.6408	$233.64	$233.65	$233.60
Purchase #4	$26.47	4.262%	$27.5982	$27.60	$27.60	$27.60
Purchase #5	$48.62	6.410%	$51.7365	$51.74	$51.75	$51.70
Purchase #6	$113.46	11.581%	$126.5998	$126.60	$126.60	$126.60
Purchase #7	$242.52	5.235%	$255.2159	$255.22	$255.20	$255.20
7 purchase totals =	$822.28		$892.3270	$892.33	$892.35	$892.30