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	$77.42	6.860%	$82.731	$82.73	$82.75	$82.70
Purchase #2	$111.51	13.171%	$126.197	$126.20	$126.20	$126.20
Purchase #3	$137.59	7.855%	$148.3977	$148.40	$148.40	$148.40
Purchase #4	$109.43	9.293%	$119.5993	$119.60	$119.60	$119.60
Purchase #5	$103.42	8.271%	$111.9739	$111.97	$111.95	$112.00
Purchase #6	$132.47	5.177%	$139.328	$139.33	$139.35	$139.30
Purchase #7	$186.93	3.794%	$194.0221	$194.02	$194.00	$194.00
7 purchase totals =	$858.77		$922.2490	$922.25	$922.25	$922.20