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	$196.69	13.801%	$223.8352	$223.84	$223.85	$223.80
Purchase #2	$207.54	4.163%	$216.1799	$216.18	$216.20	$216.20
Purchase #3	$165.85	13.814%	$188.7605	$188.76	$188.75	$188.80
Purchase #4	$123.67	11.145%	$137.453	$137.45	$137.45	$137.50
Purchase #5	$196.93	4.201%	$205.203	$205.20	$205.20	$205.20
Purchase #6	$126.83	4.366%	$132.3674	$132.37	$132.35	$132.40
Purchase #7	$18.30	7.211%	$19.6196	$19.62	$19.60	$19.60
7 purchase totals =	$1,035.81		$1,123.4186	$1,123.42	$1,123.40	$1,123.50