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	$149.31	10.545%	$165.0547	$165.05	$165.05	$165.10
Purchase #2	$59.95	5.710%	$63.3731	$63.37	$63.35	$63.40
Purchase #3	$83.35	8.649%	$90.5589	$90.56	$90.55	$90.60
Purchase #4	$104.41	6.716%	$111.4222	$111.42	$111.40	$111.40
Purchase #5	$31.78	11.409%	$35.4058	$35.41	$35.40	$35.40
Purchase #6	$202.59	13.318%	$229.5709	$229.57	$229.55	$229.60
Purchase #7	$48.86	3.772%	$50.703	$50.70	$50.70	$50.70
7 purchase totals =	$680.25		$746.0886	$746.08	$746.00	$746.20