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	$163.47	13.672%	$185.8196	$185.82	$185.80	$185.80
Purchase #2	$41.47	8.620%	$45.0447	$45.04	$45.05	$45.00
Purchase #3	$130.36	5.821%	$137.9483	$137.95	$137.95	$137.90
Purchase #4	$231.94	10.412%	$256.0896	$256.09	$256.10	$256.10
Purchase #5	$68.59	13.819%	$78.0685	$78.07	$78.05	$78.10
Purchase #6	$44.98	10.141%	$49.5414	$49.54	$49.55	$49.50
Purchase #7	$5.97	13.175%	$6.7565	$6.76	$6.75	$6.80
7 purchase totals =	$686.78		$759.2686	$759.27	$759.25	$759.20