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	$190.72	9.212%	$208.2891	$208.29	$208.30	$208.30
Purchase #2	$84.67	7.255%	$90.8128	$90.81	$90.80	$90.80
Purchase #3	$82.93	11.675%	$92.6121	$92.61	$92.60	$92.60
Purchase #4	$71.30	3.820%	$74.0237	$74.02	$74.00	$74.00
Purchase #5	$125.67	9.395%	$137.4767	$137.48	$137.50	$137.50
Purchase #6	$149.61	8.375%	$162.1398	$162.14	$162.15	$162.10
Purchase #7	$16.67	10.747%	$18.4615	$18.46	$18.45	$18.50
7 purchase totals =	$721.57		$783.8157	$783.81	$783.80	$783.80