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	$84.56	6.822%	$90.3287	$90.33	$90.35	$90.30
Purchase #2	$105.58	6.200%	$112.126	$112.13	$112.15	$112.10
Purchase #3	$10.40	11.452%	$11.591	$11.59	$11.60	$11.60
Purchase #4	$148.34	5.802%	$156.9467	$156.95	$156.95	$156.90
Purchase #5	$238.72	11.630%	$266.4831	$266.48	$266.50	$266.50
Purchase #6	$65.89	11.365%	$73.3784	$73.38	$73.40	$73.40
Purchase #7	$229.32	5.311%	$241.4992	$241.50	$241.50	$241.50
7 purchase totals =	$882.81		$952.3531	$952.36	$952.45	$952.30