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	$37.25	11.471%	$41.5229	$41.52	$41.50	$41.50
Purchase #2	$12.39	12.404%	$13.9269	$13.93	$13.95	$13.90
Purchase #3	$43.94	6.443%	$46.7711	$46.77	$46.75	$46.80
Purchase #4	$26.62	3.800%	$27.6316	$27.63	$27.65	$27.60
Purchase #5	$94.42	6.602%	$100.6536	$100.65	$100.65	$100.70
Purchase #6	$235.92	7.246%	$253.0148	$253.01	$253.00	$253.00
Purchase #7	$203.60	6.577%	$216.9908	$216.99	$217.00	$217.00
7 purchase totals =	$654.14		$700.5117	$700.50	$700.50	$700.50