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	$250.33	13.591%	$284.3524	$284.35	$284.35	$284.40
Purchase #2	$6.95	6.323%	$7.3894	$7.39	$7.40	$7.40
Purchase #3	$217.39	4.684%	$227.5725	$227.57	$227.55	$227.60
Purchase #4	$164.96	11.479%	$183.8958	$183.90	$183.90	$183.90
Purchase #5	$89.43	12.254%	$100.3888	$100.39	$100.40	$100.40
Purchase #6	$216.80	6.503%	$230.8985	$230.90	$230.90	$230.90
Purchase #7	$153.48	4.389%	$160.2162	$160.22	$160.20	$160.20
7 purchase totals =	$1,099.34		$1,194.7136	$1,194.72	$1,194.70	$1,194.80