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	$169.42	13.805%	$192.8084	$192.81	$192.80	$192.80
Purchase #2	$245.79	10.260%	$271.0081	$271.01	$271.00	$271.00
Purchase #3	$31.34	3.476%	$32.4294	$32.43	$32.45	$32.40
Purchase #4	$230.84	13.858%	$262.8298	$262.83	$262.85	$262.80
Purchase #5	$79.64	13.227%	$90.174	$90.17	$90.15	$90.20
Purchase #6	$163.77	5.415%	$172.6381	$172.64	$172.65	$172.60
Purchase #7	$7.40	10.134%	$8.1499	$8.15	$8.15	$8.10
7 purchase totals =	$928.20		$1,030.0377	$1,030.04	$1,030.05	$1,029.90