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	$146.72	3.353%	$151.6395	$151.64	$151.65	$151.60
Purchase #2	$239.78	9.639%	$262.8924	$262.89	$262.90	$262.90
Purchase #3	$224.68	5.547%	$237.143	$237.14	$237.15	$237.10
Purchase #4	$177.90	4.309%	$185.5657	$185.57	$185.55	$185.60
Purchase #5	$232.75	13.259%	$263.6103	$263.61	$263.60	$263.60
Purchase #6	$6.60	6.243%	$7.012	$7.01	$7.00	$7.00
Purchase #7	$205.97	9.383%	$225.2962	$225.30	$225.30	$225.30
7 purchase totals =	$1,234.40		$1,333.1591	$1,333.16	$1,333.15	$1,333.10