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	$216.62	4.609%	$226.604	$226.60	$226.60	$226.60
Purchase #2	$7.36	4.139%	$7.6646	$7.66	$7.65	$7.70
Purchase #3	$14.65	7.402%	$15.7344	$15.73	$15.75	$15.70
Purchase #4	$198.75	13.655%	$225.8893	$225.89	$225.90	$225.90
Purchase #5	$171.71	9.174%	$187.4627	$187.46	$187.45	$187.50
Purchase #6	$40.85	10.587%	$45.1748	$45.17	$45.15	$45.20
Purchase #7	$132.61	10.776%	$146.9001	$146.90	$146.90	$146.90
7 purchase totals =	$782.55		$855.4299	$855.41	$855.40	$855.50