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	$198.61	3.348%	$205.2595	$205.26	$205.25	$205.30
Purchase #2	$80.66	12.497%	$90.7401	$90.74	$90.75	$90.70
Purchase #3	$249.53	9.584%	$273.445	$273.45	$273.45	$273.40
Purchase #4	$37.29	4.450%	$38.9494	$38.95	$38.95	$38.90
Purchase #5	$95.49	5.257%	$100.5099	$100.51	$100.50	$100.50
Purchase #6	$131.57	10.746%	$145.7085	$145.71	$145.70	$145.70
Purchase #7	$170.62	9.538%	$186.8937	$186.89	$186.90	$186.90
7 purchase totals =	$963.77		$1,041.5061	$1,041.51	$1,041.50	$1,041.40