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	$201.75	5.654%	$213.1569	$213.16	$213.15	$213.20
Purchase #2	$96.31	10.117%	$106.0537	$106.05	$106.05	$106.10
Purchase #3	$132.71	11.128%	$147.478	$147.48	$147.50	$147.50
Purchase #4	$59.45	13.635%	$67.556	$67.56	$67.55	$67.60
Purchase #5	$229.58	11.456%	$255.8807	$255.88	$255.90	$255.90
Purchase #6	$48.77	6.281%	$51.8332	$51.83	$51.85	$51.80
Purchase #7	$23.84	3.204%	$24.6038	$24.60	$24.60	$24.60
7 purchase totals =	$792.41		$866.5623	$866.56	$866.60	$866.70