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	$67.50	9.377%	$73.8295	$73.83	$73.85	$73.80
Purchase #2	$154.95	10.854%	$171.7683	$171.77	$171.75	$171.80
Purchase #3	$14.29	11.281%	$15.9021	$15.90	$15.90	$15.90
Purchase #4	$109.75	4.530%	$114.7217	$114.72	$114.70	$114.70
Purchase #5	$250.37	5.637%	$264.4834	$264.48	$264.50	$264.50
Purchase #6	$142.34	8.105%	$153.8767	$153.88	$153.90	$153.90
Purchase #7	$145.73	3.388%	$150.6673	$150.67	$150.65	$150.70
7 purchase totals =	$884.93		$945.2490	$945.25	$945.25	$945.30