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	$66.41	9.266%	$72.5636	$72.56	$72.55	$72.60
Purchase #2	$201.76	8.601%	$219.1134	$219.11	$219.10	$219.10
Purchase #3	$238.31	7.217%	$255.5088	$255.51	$255.50	$255.50
Purchase #4	$17.63	3.828%	$18.3049	$18.30	$18.30	$18.30
Purchase #5	$34.69	11.141%	$38.5548	$38.55	$38.55	$38.60
Purchase #6	$204.78	11.117%	$227.5454	$227.55	$227.55	$227.50
Purchase #7	$230.30	5.237%	$242.3608	$242.36	$242.35	$242.40
7 purchase totals =	$993.88		$1,073.9517	$1,073.94	$1,073.90	$1,074.00