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	$141.53	11.712%	$158.106	$158.11	$158.10	$158.10
Purchase #2	$196.47	7.374%	$210.9577	$210.96	$210.95	$211.00
Purchase #3	$143.48	12.862%	$161.9344	$161.93	$161.95	$161.90
Purchase #4	$103.71	13.676%	$117.8934	$117.89	$117.90	$117.90
Purchase #5	$150.71	6.470%	$160.4609	$160.46	$160.45	$160.50
Purchase #6	$172.69	10.677%	$191.1281	$191.13	$191.15	$191.10
Purchase #7	$158.48	8.588%	$172.0903	$172.09	$172.10	$172.10
7 purchase totals =	$1,067.07		$1,172.5708	$1,172.57	$1,172.60	$1,172.60