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	$142.38	8.749%	$154.8368	$154.84	$154.85	$154.80
Purchase #2	$159.85	8.732%	$173.8081	$173.81	$173.80	$173.80
Purchase #3	$208.71	4.533%	$218.1708	$218.17	$218.15	$218.20
Purchase #4	$63.48	10.444%	$70.1099	$70.11	$70.10	$70.10
Purchase #5	$50.43	4.580%	$52.7397	$52.74	$52.75	$52.70
Purchase #6	$232.56	7.683%	$250.4276	$250.43	$250.45	$250.40
Purchase #7	$87.63	13.155%	$99.1577	$99.16	$99.15	$99.20
7 purchase totals =	$945.04		$1,019.2506	$1,019.26	$1,019.25	$1,019.20