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	$162.34	13.845%	$184.816	$184.82	$184.80	$184.80
Purchase #2	$244.87	5.813%	$259.1043	$259.10	$259.10	$259.10
Purchase #3	$161.84	3.816%	$168.0158	$168.02	$168.00	$168.00
Purchase #4	$36.94	9.206%	$40.3407	$40.34	$40.35	$40.30
Purchase #5	$203.75	10.464%	$225.0704	$225.07	$225.05	$225.10
Purchase #6	$225.68	11.165%	$250.8772	$250.88	$250.90	$250.90
Purchase #7	$42.33	3.462%	$43.7955	$43.80	$43.80	$43.80
7 purchase totals =	$1,077.75		$1,172.0199	$1,172.03	$1,172.00	$1,172.00