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	$101.35	4.531%	$105.9422	$105.94	$105.95	$105.90
Purchase #2	$130.67	10.649%	$144.585	$144.59	$144.60	$144.60
Purchase #3	$139.73	8.713%	$151.9047	$151.90	$151.90	$151.90
Purchase #4	$124.84	6.196%	$132.5751	$132.58	$132.60	$132.60
Purchase #5	$32.40	5.780%	$34.2727	$34.27	$34.25	$34.30
Purchase #6	$50.74	6.378%	$53.9762	$53.98	$54.00	$54.00
Purchase #7	$35.39	4.324%	$36.9203	$36.92	$36.90	$36.90
7 purchase totals =	$615.12		$660.1762	$660.18	$660.20	$660.20