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	$45.97	7.822%	$49.5658	$49.57	$49.55	$49.60
Purchase #2	$125.34	10.308%	$138.26	$138.26	$138.25	$138.30
Purchase #3	$190.59	13.667%	$216.6379	$216.64	$216.65	$216.60
Purchase #4	$103.96	8.622%	$112.9234	$112.92	$112.90	$112.90
Purchase #5	$170.34	11.868%	$190.556	$190.56	$190.55	$190.60
Purchase #6	$111.82	7.214%	$119.8867	$119.89	$119.90	$119.90
Purchase #7	$236.83	8.410%	$256.7474	$256.75	$256.75	$256.70
7 purchase totals =	$984.85		$1,084.5772	$1,084.59	$1,084.55	$1,084.60