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	$183.50	3.800%	$190.473	$190.47	$190.45	$190.50
Purchase #2	$82.51	10.145%	$90.8806	$90.88	$90.90	$90.90
Purchase #3	$179.29	7.164%	$192.1343	$192.13	$192.15	$192.10
Purchase #4	$66.57	11.862%	$74.4665	$74.47	$74.45	$74.50
Purchase #5	$119.89	8.849%	$130.4991	$130.50	$130.50	$130.50
Purchase #6	$212.96	4.778%	$223.1352	$223.14	$223.15	$223.10
Purchase #7	$107.69	8.784%	$117.1495	$117.15	$117.15	$117.10
7 purchase totals =	$952.41		$1,018.7382	$1,018.74	$1,018.75	$1,018.70