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	$135.25	7.871%	$145.8955	$145.90	$145.90	$145.90
Purchase #2	$36.32	7.622%	$39.0883	$39.09	$39.10	$39.10
Purchase #3	$131.89	11.400%	$146.9255	$146.93	$146.95	$146.90
Purchase #4	$11.40	4.811%	$11.9485	$11.95	$11.95	$11.90
Purchase #5	$155.95	8.243%	$168.805	$168.81	$168.80	$168.80
Purchase #6	$29.97	10.211%	$33.0302	$33.03	$33.05	$33.00
Purchase #7	$112.73	13.120%	$127.5202	$127.52	$127.50	$127.50
7 purchase totals =	$613.51		$673.2132	$673.23	$673.25	$673.10