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	$146.33	10.351%	$161.4766	$161.48	$161.50	$161.50
Purchase #2	$227.59	5.432%	$239.9527	$239.95	$239.95	$240.00
Purchase #3	$126.25	8.526%	$137.0141	$137.01	$137.00	$137.00
Purchase #4	$195.43	7.624%	$210.3296	$210.33	$210.35	$210.30
Purchase #5	$90.57	13.827%	$103.0931	$103.09	$103.10	$103.10
Purchase #6	$86.88	3.305%	$89.7514	$89.75	$89.75	$89.80
Purchase #7	$100.74	10.619%	$111.4376	$111.44	$111.45	$111.40
7 purchase totals =	$973.79		$1,053.0551	$1,053.05	$1,053.10	$1,053.10