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	$124.48	6.579%	$132.6695	$132.67	$132.65	$132.70
Purchase #2	$57.75	11.510%	$64.397	$64.40	$64.40	$64.40
Purchase #3	$151.58	13.178%	$171.5552	$171.56	$171.55	$171.60
Purchase #4	$209.59	9.858%	$230.2514	$230.25	$230.25	$230.30
Purchase #5	$51.40	6.152%	$54.5621	$54.56	$54.55	$54.60
Purchase #6	$150.26	12.238%	$168.6488	$168.65	$168.65	$168.60
Purchase #7	$11.30	5.195%	$11.887	$11.89	$11.90	$11.90
7 purchase totals =	$756.36		$833.9710	$833.98	$833.95	$834.10