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	$198.76	9.622%	$217.8847	$217.88	$217.90	$217.90
Purchase #2	$140.95	8.473%	$152.8927	$152.89	$152.90	$152.90
Purchase #3	$112.54	13.558%	$127.7982	$127.80	$127.80	$127.80
Purchase #4	$156.63	8.228%	$169.5175	$169.52	$169.50	$169.50
Purchase #5	$153.96	7.159%	$164.982	$164.98	$165.00	$165.00
Purchase #6	$51.67	6.185%	$54.8658	$54.87	$54.85	$54.90
Purchase #7	$196.81	5.458%	$207.5519	$207.55	$207.55	$207.60
7 purchase totals =	$1,011.32		$1,095.4928	$1,095.49	$1,095.50	$1,095.60