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	$10.58	10.275%	$11.6671	$11.67	$11.65	$11.70
Purchase #2	$89.26	12.855%	$100.7344	$100.73	$100.75	$100.70
Purchase #3	$208.28	4.465%	$217.5797	$217.58	$217.60	$217.60
Purchase #4	$173.41	4.711%	$181.5793	$181.58	$181.60	$181.60
Purchase #5	$12.60	3.535%	$13.0454	$13.05	$13.05	$13.00
Purchase #6	$105.57	3.784%	$109.5648	$109.56	$109.55	$109.60
Purchase #7	$75.57	3.206%	$77.9928	$77.99	$78.00	$78.00
7 purchase totals =	$675.27		$712.1635	$712.16	$712.20	$712.20