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	$119.78	11.349%	$133.3738	$133.37	$133.35	$133.40
Purchase #2	$214.82	3.862%	$223.1163	$223.12	$223.10	$223.10
Purchase #3	$87.85	6.873%	$93.8879	$93.89	$93.90	$93.90
Purchase #4	$102.41	8.832%	$111.4549	$111.45	$111.45	$111.50
Purchase #5	$81.34	4.510%	$85.0084	$85.01	$85.00	$85.00
Purchase #6	$98.63	13.138%	$111.588	$111.59	$111.60	$111.60
Purchase #7	$193.82	4.851%	$203.2222	$203.22	$203.20	$203.20
7 purchase totals =	$898.65		$961.6515	$961.65	$961.60	$961.70