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	$78.67	11.534%	$87.7438	$87.74	$87.75	$87.70
Purchase #2	$61.85	13.848%	$70.415	$70.42	$70.40	$70.40
Purchase #3	$111.88	13.630%	$127.1292	$127.13	$127.15	$127.10
Purchase #4	$196.63	6.248%	$208.9154	$208.92	$208.90	$208.90
Purchase #5	$217.37	5.542%	$229.4166	$229.42	$229.40	$229.40
Purchase #6	$48.54	12.633%	$54.6721	$54.67	$54.65	$54.70
Purchase #7	$34.96	12.787%	$39.4303	$39.43	$39.45	$39.40
7 purchase totals =	$749.90		$817.7224	$817.73	$817.70	$817.60