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	$6.94	7.684%	$7.4733	$7.47	$7.45	$7.50
Purchase #2	$171.87	10.719%	$190.2927	$190.29	$190.30	$190.30
Purchase #3	$48.96	8.156%	$52.9532	$52.95	$52.95	$53.00
Purchase #4	$208.53	11.298%	$232.0897	$232.09	$232.10	$232.10
Purchase #5	$93.54	13.182%	$105.8704	$105.87	$105.85	$105.90
Purchase #6	$53.73	3.331%	$55.5197	$55.52	$55.50	$55.50
Purchase #7	$183.84	13.486%	$208.6327	$208.63	$208.65	$208.60
7 purchase totals =	$767.41		$852.8317	$852.82	$852.80	$852.90