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	$161.54	7.866%	$174.2467	$174.25	$174.25	$174.20
Purchase #2	$188.89	11.136%	$209.9248	$209.92	$209.90	$209.90
Purchase #3	$46.85	8.704%	$50.9278	$50.93	$50.95	$50.90
Purchase #4	$143.92	4.335%	$150.1589	$150.16	$150.15	$150.20
Purchase #5	$33.53	12.134%	$37.5985	$37.60	$37.60	$37.60
Purchase #6	$239.52	9.795%	$262.981	$262.98	$263.00	$263.00
Purchase #7	$67.82	3.639%	$70.288	$70.29	$70.30	$70.30
7 purchase totals =	$882.07		$956.1257	$956.13	$956.15	$956.10