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	$181.49	10.457%	$200.4684	$200.47	$200.45	$200.50
Purchase #2	$9.72	10.864%	$10.776	$10.78	$10.80	$10.80
Purchase #3	$31.53	10.684%	$34.8987	$34.90	$34.90	$34.90
Purchase #4	$89.33	5.835%	$94.5424	$94.54	$94.55	$94.50
Purchase #5	$50.62	3.217%	$52.2484	$52.25	$52.25	$52.20
Purchase #6	$134.28	9.670%	$147.2649	$147.26	$147.25	$147.30
Purchase #7	$182.70	4.147%	$190.2766	$190.28	$190.30	$190.30
7 purchase totals =	$679.67		$730.4754	$730.48	$730.50	$730.50