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	$83.76	3.218%	$86.4554	$86.46	$86.45	$86.50
Purchase #2	$38.56	11.545%	$43.0118	$43.01	$43.00	$43.00
Purchase #3	$172.61	5.273%	$181.7117	$181.71	$181.70	$181.70
Purchase #4	$160.59	9.865%	$176.4322	$176.43	$176.45	$176.40
Purchase #5	$113.73	5.428%	$119.9033	$119.90	$119.90	$119.90
Purchase #6	$70.86	13.228%	$80.2334	$80.23	$80.25	$80.20
Purchase #7	$86.27	12.596%	$97.1366	$97.14	$97.15	$97.10
7 purchase totals =	$726.38		$784.8844	$784.88	$784.90	$784.80