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	$131.52	11.380%	$146.487	$146.49	$146.50	$146.50
Purchase #2	$138.95	12.510%	$156.3326	$156.33	$156.35	$156.30
Purchase #3	$218.29	5.302%	$229.8637	$229.86	$229.85	$229.90
Purchase #4	$224.70	13.773%	$255.6479	$255.65	$255.65	$255.60
Purchase #5	$183.60	9.397%	$200.8529	$200.85	$200.85	$200.90
Purchase #6	$159.50	13.365%	$180.8172	$180.82	$180.80	$180.80
Purchase #7	$37.72	11.328%	$41.9929	$41.99	$42.00	$42.00
7 purchase totals =	$1,094.28		$1,211.9942	$1,211.99	$1,212.00	$1,212.00