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	$184.57	11.808%	$206.364	$206.36	$206.35	$206.40
Purchase #2	$229.61	12.714%	$258.8026	$258.80	$258.80	$258.80
Purchase #3	$124.98	5.140%	$131.404	$131.40	$131.40	$131.40
Purchase #4	$140.93	6.826%	$150.5499	$150.55	$150.55	$150.50
Purchase #5	$55.86	13.349%	$63.3168	$63.32	$63.30	$63.30
Purchase #6	$143.59	8.867%	$156.3221	$156.32	$156.30	$156.30
Purchase #7	$31.53	10.652%	$34.8886	$34.89	$34.90	$34.90
7 purchase totals =	$911.07		$1,001.6480	$1,001.64	$1,001.60	$1,001.60