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	$144.77	4.203%	$150.8547	$150.85	$150.85	$150.90
Purchase #2	$46.37	4.706%	$48.5522	$48.55	$48.55	$48.60
Purchase #3	$125.92	4.712%	$131.8534	$131.85	$131.85	$131.90
Purchase #4	$170.76	13.664%	$194.0926	$194.09	$194.10	$194.10
Purchase #5	$7.38	8.492%	$8.0067	$8.01	$8.00	$8.00
Purchase #6	$30.36	13.668%	$34.5096	$34.51	$34.50	$34.50
Purchase #7	$152.54	6.599%	$162.6061	$162.61	$162.60	$162.60
7 purchase totals =	$678.10		$730.4753	$730.47	$730.45	$730.60