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	$92.73	7.475%	$99.6616	$99.66	$99.65	$99.70
Purchase #2	$149.59	12.473%	$168.2484	$168.25	$168.25	$168.20
Purchase #3	$87.47	9.241%	$95.5531	$95.55	$95.55	$95.60
Purchase #4	$171.94	4.423%	$179.5449	$179.54	$179.55	$179.50
Purchase #5	$231.85	13.863%	$263.9914	$263.99	$264.00	$264.00
Purchase #6	$247.50	5.492%	$261.0927	$261.09	$261.10	$261.10
Purchase #7	$127.45	7.756%	$137.335	$137.34	$137.35	$137.30
7 purchase totals =	$1,108.53		$1,205.4271	$1,205.42	$1,205.45	$1,205.40