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	$210.92	4.105%	$219.5783	$219.58	$219.60	$219.60
Purchase #2	$106.27	10.743%	$117.6866	$117.69	$117.70	$117.70
Purchase #3	$147.54	6.121%	$156.5709	$156.57	$156.55	$156.60
Purchase #4	$225.47	13.344%	$255.5567	$255.56	$255.55	$255.60
Purchase #5	$60.72	8.545%	$65.9085	$65.91	$65.90	$65.90
Purchase #6	$17.66	4.820%	$18.5112	$18.51	$18.50	$18.50
Purchase #7	$188.29	9.169%	$205.5543	$205.55	$205.55	$205.60
7 purchase totals =	$956.87		$1,039.3665	$1,039.37	$1,039.35	$1,039.50