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	$189.53	13.846%	$215.7723	$215.77	$215.75	$215.80
Purchase #2	$203.73	5.855%	$215.6584	$215.66	$215.65	$215.70
Purchase #3	$79.81	7.296%	$85.6329	$85.63	$85.65	$85.60
Purchase #4	$60.35	6.801%	$64.4544	$64.45	$64.45	$64.50
Purchase #5	$164.70	5.404%	$173.6004	$173.60	$173.60	$173.60
Purchase #6	$37.98	12.487%	$42.7226	$42.72	$42.70	$42.70
Purchase #7	$127.47	7.621%	$137.1845	$137.18	$137.20	$137.20
7 purchase totals =	$863.57		$935.0255	$935.01	$935.00	$935.10