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	$153.80	11.181%	$170.9964	$171.00	$171.00	$171.00
Purchase #2	$178.26	6.586%	$190.0002	$190.00	$190.00	$190.00
Purchase #3	$72.30	12.581%	$81.3961	$81.40	$81.40	$81.40
Purchase #4	$111.88	13.361%	$126.8283	$126.83	$126.85	$126.80
Purchase #5	$33.32	13.545%	$37.8332	$37.83	$37.85	$37.80
Purchase #6	$226.53	6.805%	$241.9454	$241.95	$241.95	$241.90
Purchase #7	$155.66	3.500%	$161.1081	$161.11	$161.10	$161.10
7 purchase totals =	$931.75		$1,010.1077	$1,010.12	$1,010.15	$1,010.00