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	$210.94	6.607%	$224.8768	$224.88	$224.90	$224.90
Purchase #2	$215.39	9.505%	$235.8628	$235.86	$235.85	$235.90
Purchase #3	$33.83	6.342%	$35.9755	$35.98	$36.00	$36.00
Purchase #4	$175.53	9.431%	$192.0842	$192.08	$192.10	$192.10
Purchase #5	$98.38	13.517%	$111.678	$111.68	$111.70	$111.70
Purchase #6	$74.60	5.746%	$78.8865	$78.89	$78.90	$78.90
Purchase #7	$195.82	11.333%	$218.0123	$218.01	$218.00	$218.00
7 purchase totals =	$1,004.49		$1,097.3761	$1,097.38	$1,097.45	$1,097.50