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	$105.34	11.617%	$117.5773	$117.58	$117.60	$117.60
Purchase #2	$136.28	11.182%	$151.5188	$151.52	$151.50	$151.50
Purchase #3	$27.30	13.634%	$31.0221	$31.02	$31.00	$31.00
Purchase #4	$203.43	3.193%	$209.9255	$209.93	$209.95	$209.90
Purchase #5	$52.99	5.358%	$55.8292	$55.83	$55.85	$55.80
Purchase #6	$85.97	5.209%	$90.4482	$90.45	$90.45	$90.40
Purchase #7	$193.34	13.476%	$219.3945	$219.39	$219.40	$219.40
7 purchase totals =	$804.65		$875.7156	$875.72	$875.75	$875.60