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	$66.54	9.483%	$72.85	$72.85	$72.85	$72.90
Purchase #2	$38.37	13.203%	$43.436	$43.44	$43.45	$43.40
Purchase #3	$151.83	11.339%	$169.046	$169.05	$169.05	$169.00
Purchase #4	$30.72	11.342%	$34.2043	$34.20	$34.20	$34.20
Purchase #5	$201.95	11.220%	$224.6088	$224.61	$224.60	$224.60
Purchase #6	$196.33	12.861%	$221.58	$221.58	$221.60	$221.60
Purchase #7	$116.53	6.838%	$124.4983	$124.50	$124.50	$124.50
7 purchase totals =	$802.27		$890.2234	$890.23	$890.25	$890.20