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	$127.95	9.152%	$139.66	$139.66	$139.65	$139.70
Purchase #2	$153.99	11.700%	$172.0068	$172.01	$172.00	$172.00
Purchase #3	$45.61	4.259%	$47.5525	$47.55	$47.55	$47.60
Purchase #4	$206.78	11.157%	$229.8504	$229.85	$229.85	$229.90
Purchase #5	$226.74	9.456%	$248.1805	$248.18	$248.20	$248.20
Purchase #6	$37.31	11.378%	$41.5551	$41.56	$41.55	$41.60
Purchase #7	$216.45	5.570%	$228.5063	$228.51	$228.50	$228.50
7 purchase totals =	$1,014.83		$1,107.3116	$1,107.32	$1,107.30	$1,107.50