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	$67.51	5.561%	$71.2642	$71.26	$71.25	$71.30
Purchase #2	$20.85	7.523%	$22.4185	$22.42	$22.40	$22.40
Purchase #3	$227.48	12.604%	$256.1516	$256.15	$256.15	$256.20
Purchase #4	$127.77	12.465%	$143.6965	$143.70	$143.70	$143.70
Purchase #5	$142.66	13.454%	$161.8535	$161.85	$161.85	$161.90
Purchase #6	$49.75	6.759%	$53.1126	$53.11	$53.10	$53.10
Purchase #7	$38.35	6.632%	$40.8934	$40.89	$40.90	$40.90
7 purchase totals =	$674.37		$749.3903	$749.38	$749.35	$749.50