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	$36.63	11.309%	$40.7725	$40.77	$40.75	$40.80
Purchase #2	$52.31	5.403%	$55.1363	$55.14	$55.15	$55.10
Purchase #3	$217.93	12.267%	$244.6635	$244.66	$244.65	$244.70
Purchase #4	$178.83	4.534%	$186.9382	$186.94	$186.95	$186.90
Purchase #5	$184.57	8.141%	$199.5958	$199.60	$199.60	$199.60
Purchase #6	$238.48	4.692%	$249.6695	$249.67	$249.65	$249.70
Purchase #7	$37.40	9.378%	$40.9074	$40.91	$40.90	$40.90
7 purchase totals =	$946.15		$1,017.6832	$1,017.69	$1,017.65	$1,017.70