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	$242.34	11.873%	$271.113	$271.11	$271.10	$271.10
Purchase #2	$171.51	5.483%	$180.9139	$180.91	$180.90	$180.90
Purchase #3	$190.73	13.635%	$216.736	$216.74	$216.75	$216.70
Purchase #4	$205.75	4.770%	$215.5643	$215.56	$215.55	$215.60
Purchase #5	$82.60	13.405%	$93.6725	$93.67	$93.65	$93.70
Purchase #6	$157.79	9.332%	$172.515	$172.52	$172.50	$172.50
Purchase #7	$10.74	12.249%	$12.0555	$12.06	$12.05	$12.10
7 purchase totals =	$1,061.46		$1,162.5702	$1,162.57	$1,162.50	$1,162.60