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	$232.33	4.473%	$242.7221	$242.72	$242.70	$242.70
Purchase #2	$129.89	11.147%	$144.3688	$144.37	$144.35	$144.40
Purchase #3	$11.47	13.620%	$13.0322	$13.03	$13.05	$13.00
Purchase #4	$13.42	8.118%	$14.5094	$14.51	$14.50	$14.50
Purchase #5	$136.71	13.844%	$155.6361	$155.64	$155.65	$155.60
Purchase #6	$144.59	9.590%	$158.4562	$158.46	$158.45	$158.50
Purchase #7	$117.94	4.812%	$123.6153	$123.62	$123.60	$123.60
7 purchase totals =	$786.35		$852.3401	$852.35	$852.30	$852.30