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	$78.86	8.723%	$85.739	$85.74	$85.75	$85.70
Purchase #2	$247.34	8.847%	$269.2222	$269.22	$269.20	$269.20
Purchase #3	$231.87	11.444%	$258.4052	$258.41	$258.40	$258.40
Purchase #4	$152.93	12.481%	$172.0172	$172.02	$172.00	$172.00
Purchase #5	$106.90	5.498%	$112.7774	$112.78	$112.80	$112.80
Purchase #6	$64.51	3.667%	$66.8756	$66.88	$66.90	$66.90
Purchase #7	$86.67	13.778%	$98.6114	$98.61	$98.60	$98.60
7 purchase totals =	$969.08		$1,063.6480	$1,063.66	$1,063.65	$1,063.60