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	$209.44	4.786%	$219.4638	$219.46	$219.45	$219.50
Purchase #2	$47.63	6.724%	$50.8326	$50.83	$50.85	$50.80
Purchase #3	$38.60	5.568%	$40.7492	$40.75	$40.75	$40.70
Purchase #4	$26.34	8.764%	$28.6484	$28.65	$28.65	$28.60
Purchase #5	$100.48	11.406%	$111.9407	$111.94	$111.95	$111.90
Purchase #6	$171.90	13.216%	$194.6183	$194.62	$194.60	$194.60
Purchase #7	$217.82	6.292%	$231.5252	$231.53	$231.55	$231.50
7 purchase totals =	$812.21		$877.7782	$877.78	$877.80	$877.60