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	$95.59	5.141%	$100.5043	$100.50	$100.50	$100.50
Purchase #2	$208.40	5.628%	$220.1288	$220.13	$220.15	$220.10
Purchase #3	$240.90	8.775%	$262.039	$262.04	$262.05	$262.00
Purchase #4	$132.73	6.769%	$141.7145	$141.71	$141.70	$141.70
Purchase #5	$80.61	6.270%	$85.6642	$85.66	$85.65	$85.70
Purchase #6	$20.29	4.742%	$21.2522	$21.25	$21.25	$21.30
Purchase #7	$173.52	12.704%	$195.564	$195.56	$195.55	$195.60
7 purchase totals =	$952.04		$1,026.8670	$1,026.85	$1,026.85	$1,026.90