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	$100.26	5.871%	$106.1463	$106.15	$106.15	$106.10
Purchase #2	$174.94	8.622%	$190.0233	$190.02	$190.00	$190.00
Purchase #3	$164.78	4.613%	$172.3813	$172.38	$172.40	$172.40
Purchase #4	$103.25	10.819%	$114.4206	$114.42	$114.40	$114.40
Purchase #5	$7.73	9.703%	$8.48	$8.48	$8.50	$8.50
Purchase #6	$40.75	6.465%	$43.3845	$43.38	$43.40	$43.40
Purchase #7	$119.34	6.491%	$127.0864	$127.09	$127.10	$127.10
7 purchase totals =	$711.05		$761.9224	$761.92	$761.95	$761.90