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	$171.79	12.317%	$192.9494	$192.95	$192.95	$192.90
Purchase #2	$40.43	12.242%	$45.3794	$45.38	$45.40	$45.40
Purchase #3	$199.43	10.603%	$220.5756	$220.58	$220.60	$220.60
Purchase #4	$53.89	4.575%	$56.3555	$56.36	$56.35	$56.40
Purchase #5	$232.50	13.692%	$264.3339	$264.33	$264.35	$264.30
Purchase #6	$126.37	3.238%	$130.4619	$130.46	$130.45	$130.50
Purchase #7	$228.43	11.569%	$254.8571	$254.86	$254.85	$254.90
7 purchase totals =	$1,052.84		$1,164.9128	$1,164.92	$1,164.95	$1,165.00