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	$63.49	10.198%	$69.9647	$69.96	$69.95	$70.00
Purchase #2	$37.37	11.810%	$41.7834	$41.78	$41.80	$41.80
Purchase #3	$194.73	13.226%	$220.485	$220.49	$220.50	$220.50
Purchase #4	$67.83	6.158%	$72.007	$72.01	$72.00	$72.00
Purchase #5	$40.36	13.687%	$45.8841	$45.88	$45.90	$45.90
Purchase #6	$237.54	13.561%	$269.7528	$269.75	$269.75	$269.80
Purchase #7	$217.34	6.675%	$231.8474	$231.85	$231.85	$231.80
7 purchase totals =	$858.66		$951.7244	$951.72	$951.75	$951.80