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	$55.73	6.312%	$59.2477	$59.25	$59.25	$59.20
Purchase #2	$176.92	8.683%	$192.282	$192.28	$192.30	$192.30
Purchase #3	$19.51	6.786%	$20.8339	$20.83	$20.85	$20.80
Purchase #4	$110.43	10.785%	$122.3399	$122.34	$122.35	$122.30
Purchase #5	$234.65	9.102%	$256.0078	$256.01	$256.00	$256.00
Purchase #6	$118.50	4.519%	$123.855	$123.86	$123.85	$123.90
Purchase #7	$72.87	7.228%	$78.137	$78.14	$78.15	$78.10
7 purchase totals =	$788.61		$852.7033	$852.71	$852.75	$852.60