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	$216.57	8.690%	$235.3899	$235.39	$235.40	$235.40
Purchase #2	$9.84	4.499%	$10.2827	$10.28	$10.30	$10.30
Purchase #3	$183.69	3.130%	$189.4395	$189.44	$189.45	$189.40
Purchase #4	$102.48	9.357%	$112.0691	$112.07	$112.05	$112.10
Purchase #5	$37.34	9.577%	$40.9161	$40.92	$40.90	$40.90
Purchase #6	$161.95	6.774%	$172.9205	$172.92	$172.90	$172.90
Purchase #7	$158.40	4.732%	$165.8955	$165.90	$165.90	$165.90
7 purchase totals =	$870.27		$926.9133	$926.92	$926.90	$926.90