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	$145.36	4.847%	$152.4056	$152.41	$152.40	$152.40
Purchase #2	$185.43	12.294%	$208.2268	$208.23	$208.25	$208.20
Purchase #3	$185.80	6.791%	$198.4177	$198.42	$198.40	$198.40
Purchase #4	$25.85	7.859%	$27.8816	$27.88	$27.90	$27.90
Purchase #5	$15.74	10.536%	$17.3984	$17.40	$17.40	$17.40
Purchase #6	$37.58	8.579%	$40.804	$40.80	$40.80	$40.80
Purchase #7	$155.30	4.583%	$162.4174	$162.42	$162.40	$162.40
7 purchase totals =	$751.06		$807.5515	$807.56	$807.55	$807.50