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	$53.55	12.365%	$60.1715	$60.17	$60.15	$60.20
Purchase #2	$187.83	13.130%	$212.4921	$212.49	$212.50	$212.50
Purchase #3	$42.71	13.492%	$48.4724	$48.47	$48.45	$48.50
Purchase #4	$221.78	12.767%	$250.0947	$250.09	$250.10	$250.10
Purchase #5	$213.40	7.532%	$229.4733	$229.47	$229.45	$229.50
Purchase #6	$221.45	11.675%	$247.3043	$247.30	$247.30	$247.30
Purchase #7	$60.69	7.830%	$65.442	$65.44	$65.45	$65.40
7 purchase totals =	$1,001.41		$1,113.4503	$1,113.43	$1,113.40	$1,113.50