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	$29.46	11.862%	$32.9545	$32.95	$32.95	$33.00
Purchase #2	$154.60	6.715%	$164.9814	$164.98	$165.00	$165.00
Purchase #3	$37.73	9.342%	$41.2547	$41.25	$41.25	$41.30
Purchase #4	$227.87	12.745%	$256.912	$256.91	$256.90	$256.90
Purchase #5	$62.50	12.766%	$70.4788	$70.48	$70.50	$70.50
Purchase #6	$152.71	13.385%	$173.1502	$173.15	$173.15	$173.20
Purchase #7	$40.88	8.808%	$44.4807	$44.48	$44.50	$44.50
7 purchase totals =	$705.75		$784.2123	$784.20	$784.25	$784.40