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	$119.97	8.553%	$130.231	$130.23	$130.25	$130.20
Purchase #2	$141.90	3.274%	$146.5458	$146.55	$146.55	$146.50
Purchase #3	$141.84	4.237%	$147.8498	$147.85	$147.85	$147.80
Purchase #4	$132.96	13.293%	$150.6344	$150.63	$150.65	$150.60
Purchase #5	$127.60	11.162%	$141.8427	$141.84	$141.85	$141.80
Purchase #6	$47.87	9.873%	$52.5962	$52.60	$52.60	$52.60
Purchase #7	$205.84	4.868%	$215.8603	$215.86	$215.85	$215.90
7 purchase totals =	$917.98		$985.5602	$985.56	$985.60	$985.40