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	$133.55	8.534%	$144.9472	$144.95	$144.95	$144.90
Purchase #2	$45.56	11.654%	$50.8696	$50.87	$50.85	$50.90
Purchase #3	$164.71	8.683%	$179.0118	$179.01	$179.00	$179.00
Purchase #4	$46.79	12.369%	$52.5775	$52.58	$52.60	$52.60
Purchase #5	$149.80	8.180%	$162.0536	$162.05	$162.05	$162.10
Purchase #6	$41.33	3.105%	$42.6133	$42.61	$42.60	$42.60
Purchase #7	$64.90	7.174%	$69.5559	$69.56	$69.55	$69.60
7 purchase totals =	$646.64		$701.6289	$701.63	$701.60	$701.70