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	$233.86	4.157%	$243.5816	$243.58	$243.60	$243.60
Purchase #2	$26.80	9.531%	$29.3543	$29.35	$29.35	$29.40
Purchase #3	$141.95	7.605%	$152.7453	$152.75	$152.75	$152.70
Purchase #4	$29.81	9.301%	$32.5826	$32.58	$32.60	$32.60
Purchase #5	$41.55	8.382%	$45.0327	$45.03	$45.05	$45.00
Purchase #6	$157.60	9.285%	$172.2332	$172.23	$172.25	$172.20
Purchase #7	$230.83	11.235%	$256.7638	$256.76	$256.75	$256.80
7 purchase totals =	$862.40		$932.2935	$932.28	$932.35	$932.30