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	$125.62	8.784%	$136.6545	$136.65	$136.65	$136.70
Purchase #2	$90.25	10.333%	$99.5755	$99.58	$99.60	$99.60
Purchase #3	$11.90	7.821%	$12.8307	$12.83	$12.85	$12.80
Purchase #4	$164.72	7.217%	$176.6078	$176.61	$176.60	$176.60
Purchase #5	$118.58	6.447%	$126.2249	$126.22	$126.20	$126.20
Purchase #6	$192.88	4.108%	$200.8035	$200.80	$200.80	$200.80
Purchase #7	$106.59	12.465%	$119.8764	$119.88	$119.90	$119.90
7 purchase totals =	$810.54		$872.5733	$872.57	$872.60	$872.60