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	$105.86	11.340%	$117.8645	$117.86	$117.85	$117.90
Purchase #2	$48.40	8.426%	$52.4782	$52.48	$52.50	$52.50
Purchase #3	$81.54	6.576%	$86.9021	$86.90	$86.90	$86.90
Purchase #4	$74.52	9.366%	$81.4995	$81.50	$81.50	$81.50
Purchase #5	$140.42	4.449%	$146.6673	$146.67	$146.65	$146.70
Purchase #6	$233.57	5.366%	$246.1034	$246.10	$246.10	$246.10
Purchase #7	$150.43	12.321%	$168.9645	$168.96	$168.95	$169.00
7 purchase totals =	$834.74		$900.4795	$900.47	$900.45	$900.60