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	$137.36	5.176%	$144.4698	$144.47	$144.45	$144.50
Purchase #2	$199.66	11.360%	$222.3414	$222.34	$222.35	$222.30
Purchase #3	$138.97	10.290%	$153.27	$153.27	$153.25	$153.30
Purchase #4	$138.43	12.705%	$156.0175	$156.02	$156.00	$156.00
Purchase #5	$149.95	12.102%	$168.0969	$168.10	$168.10	$168.10
Purchase #6	$242.51	5.224%	$255.1787	$255.18	$255.20	$255.20
Purchase #7	$239.49	12.693%	$269.8885	$269.89	$269.90	$269.90
7 purchase totals =	$1,246.37		$1,369.2628	$1,369.27	$1,369.25	$1,369.30