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	$127.54	7.340%	$136.9014	$136.90	$136.90	$136.90
Purchase #2	$168.31	4.179%	$175.3437	$175.34	$175.35	$175.30
Purchase #3	$62.89	3.240%	$64.9276	$64.93	$64.95	$64.90
Purchase #4	$99.66	11.465%	$111.086	$111.09	$111.10	$111.10
Purchase #5	$34.99	3.788%	$36.3154	$36.32	$36.30	$36.30
Purchase #6	$100.27	13.401%	$113.7072	$113.71	$113.70	$113.70
Purchase #7	$98.43	9.325%	$107.6086	$107.61	$107.60	$107.60
7 purchase totals =	$692.09		$745.8899	$745.90	$745.90	$745.80