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	$234.68	9.555%	$257.1037	$257.10	$257.10	$257.10
Purchase #2	$218.68	7.262%	$234.5605	$234.56	$234.55	$234.60
Purchase #3	$140.81	6.867%	$150.4794	$150.48	$150.50	$150.50
Purchase #4	$40.88	12.414%	$45.9548	$45.95	$45.95	$46.00
Purchase #5	$202.62	9.759%	$222.3937	$222.39	$222.40	$222.40
Purchase #6	$95.54	5.357%	$100.6581	$100.66	$100.65	$100.70
Purchase #7	$33.63	5.215%	$35.3838	$35.38	$35.40	$35.40
7 purchase totals =	$966.84		$1,046.5340	$1,046.52	$1,046.55	$1,046.70