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	$224.72	8.173%	$243.0864	$243.09	$243.10	$243.10
Purchase #2	$72.89	12.524%	$82.0187	$82.02	$82.00	$82.00
Purchase #3	$11.46	6.326%	$12.185	$12.19	$12.20	$12.20
Purchase #4	$145.57	11.173%	$161.8345	$161.83	$161.85	$161.80
Purchase #5	$232.72	10.352%	$256.8112	$256.81	$256.80	$256.80
Purchase #6	$117.90	5.593%	$124.4941	$124.49	$124.50	$124.50
Purchase #7	$127.40	9.106%	$139.001	$139.00	$139.00	$139.00
7 purchase totals =	$932.66		$1,019.4309	$1,019.43	$1,019.45	$1,019.40