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	$205.48	7.835%	$221.5794	$221.58	$221.60	$221.60
Purchase #2	$138.74	4.769%	$145.3565	$145.36	$145.35	$145.40
Purchase #3	$202.81	9.540%	$222.1581	$222.16	$222.15	$222.20
Purchase #4	$146.59	13.500%	$166.3797	$166.38	$166.40	$166.40
Purchase #5	$39.46	7.335%	$42.3544	$42.35	$42.35	$42.40
Purchase #6	$199.84	11.139%	$222.1002	$222.10	$222.10	$222.10
Purchase #7	$84.81	9.858%	$93.1706	$93.17	$93.15	$93.20
7 purchase totals =	$1,017.73		$1,113.0989	$1,113.10	$1,113.10	$1,113.30