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	$46.93	11.221%	$52.196	$52.20	$52.20	$52.20
Purchase #2	$205.82	6.866%	$219.9516	$219.95	$219.95	$220.00
Purchase #3	$69.70	12.844%	$78.6523	$78.65	$78.65	$78.70
Purchase #4	$219.79	12.372%	$246.9824	$246.98	$247.00	$247.00
Purchase #5	$153.75	6.667%	$164.0005	$164.00	$164.00	$164.00
Purchase #6	$99.43	12.534%	$111.8926	$111.89	$111.90	$111.90
Purchase #7	$94.85	6.664%	$101.1708	$101.17	$101.15	$101.20
7 purchase totals =	$890.27		$974.8462	$974.84	$974.85	$975.00