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	$155.33	12.874%	$175.3272	$175.33	$175.35	$175.30
Purchase #2	$48.80	8.335%	$52.8675	$52.87	$52.85	$52.90
Purchase #3	$173.97	5.612%	$183.7332	$183.73	$183.75	$183.70
Purchase #4	$192.78	12.510%	$216.8968	$216.90	$216.90	$216.90
Purchase #5	$100.37	13.130%	$113.5486	$113.55	$113.55	$113.50
Purchase #6	$146.31	10.367%	$161.478	$161.48	$161.50	$161.50
Purchase #7	$65.42	10.427%	$72.2413	$72.24	$72.25	$72.20
7 purchase totals =	$882.98		$976.0926	$976.10	$976.15	$976.00