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	$58.78	13.777%	$66.8781	$66.88	$66.90	$66.90
Purchase #2	$216.35	13.194%	$244.8952	$244.90	$244.90	$244.90
Purchase #3	$207.36	9.792%	$227.6647	$227.66	$227.65	$227.70
Purchase #4	$32.49	6.405%	$34.571	$34.57	$34.55	$34.60
Purchase #5	$54.51	9.670%	$59.7811	$59.78	$59.80	$59.80
Purchase #6	$37.98	5.820%	$40.1904	$40.19	$40.20	$40.20
Purchase #7	$228.89	13.323%	$259.385	$259.39	$259.40	$259.40
7 purchase totals =	$836.36		$933.3655	$933.37	$933.40	$933.50