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	$64.74	12.276%	$72.6875	$72.69	$72.70	$72.70
Purchase #2	$126.36	9.120%	$137.884	$137.88	$137.90	$137.90
Purchase #3	$202.26	5.813%	$214.0174	$214.02	$214.00	$214.00
Purchase #4	$34.51	11.523%	$38.4866	$38.49	$38.50	$38.50
Purchase #5	$30.54	6.435%	$32.5052	$32.51	$32.50	$32.50
Purchase #6	$231.66	7.868%	$249.887	$249.89	$249.90	$249.90
Purchase #7	$29.60	11.188%	$32.9116	$32.91	$32.90	$32.90
7 purchase totals =	$719.67		$778.3793	$778.39	$778.40	$778.40