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	$181.67	6.170%	$192.879	$192.88	$192.90	$192.90
Purchase #2	$117.94	11.712%	$131.7531	$131.75	$131.75	$131.80
Purchase #3	$62.68	13.393%	$71.0747	$71.07	$71.05	$71.10
Purchase #4	$115.88	9.153%	$126.4865	$126.49	$126.50	$126.50
Purchase #5	$189.65	3.663%	$196.5969	$196.60	$196.60	$196.60
Purchase #6	$125.82	8.163%	$136.0907	$136.09	$136.10	$136.10
Purchase #7	$33.57	10.845%	$37.2107	$37.21	$37.20	$37.20
7 purchase totals =	$827.21		$892.0916	$892.09	$892.10	$892.20