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	$201.86	10.439%	$222.9322	$222.93	$222.95	$222.90
Purchase #2	$232.42	7.340%	$249.4796	$249.48	$249.50	$249.50
Purchase #3	$53.25	13.590%	$60.4867	$60.49	$60.50	$60.50
Purchase #4	$33.66	3.871%	$34.963	$34.96	$34.95	$35.00
Purchase #5	$164.76	5.156%	$173.255	$173.26	$173.25	$173.30
Purchase #6	$66.68	6.690%	$71.1409	$71.14	$71.15	$71.10
Purchase #7	$125.38	11.334%	$139.5906	$139.59	$139.60	$139.60
7 purchase totals =	$878.01		$951.8480	$951.85	$951.90	$951.90