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	$203.36	7.243%	$218.0894	$218.09	$218.10	$218.10
Purchase #2	$132.92	8.711%	$144.4987	$144.50	$144.50	$144.50
Purchase #3	$109.78	7.857%	$118.4054	$118.41	$118.40	$118.40
Purchase #4	$6.54	7.487%	$7.0296	$7.03	$7.05	$7.00
Purchase #5	$13.84	7.507%	$14.879	$14.88	$14.90	$14.90
Purchase #6	$117.61	12.156%	$131.9067	$131.91	$131.90	$131.90
Purchase #7	$84.54	7.349%	$90.7528	$90.75	$90.75	$90.80
7 purchase totals =	$668.59		$725.5616	$725.57	$725.60	$725.60