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	$76.25	12.153%	$85.5167	$85.52	$85.50	$85.50
Purchase #2	$205.36	8.400%	$222.6102	$222.61	$222.60	$222.60
Purchase #3	$113.62	13.172%	$128.586	$128.59	$128.60	$128.60
Purchase #4	$34.44	9.822%	$37.8227	$37.82	$37.80	$37.80
Purchase #5	$158.65	9.460%	$173.6583	$173.66	$173.65	$173.70
Purchase #6	$87.50	13.543%	$99.3501	$99.35	$99.35	$99.40
Purchase #7	$206.71	7.802%	$222.8375	$222.84	$222.85	$222.80
7 purchase totals =	$882.53		$970.3815	$970.39	$970.35	$970.40