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	$31.75	10.108%	$34.9593	$34.96	$34.95	$35.00
Purchase #2	$37.45	8.375%	$40.5864	$40.59	$40.60	$40.60
Purchase #3	$232.90	5.132%	$244.8524	$244.85	$244.85	$244.90
Purchase #4	$179.84	6.502%	$191.5332	$191.53	$191.55	$191.50
Purchase #5	$106.81	4.455%	$111.5684	$111.57	$111.55	$111.60
Purchase #6	$23.45	10.663%	$25.9505	$25.95	$25.95	$26.00
Purchase #7	$123.81	8.730%	$134.6186	$134.62	$134.60	$134.60
7 purchase totals =	$736.01		$784.0688	$784.07	$784.05	$784.20