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	$56.83	4.712%	$59.5078	$59.51	$59.50	$59.50
Purchase #2	$213.36	5.526%	$225.1503	$225.15	$225.15	$225.20
Purchase #3	$5.32	9.210%	$5.81	$5.81	$5.80	$5.80
Purchase #4	$109.32	6.591%	$116.5253	$116.53	$116.55	$116.50
Purchase #5	$140.45	5.265%	$147.8447	$147.84	$147.85	$147.80
Purchase #6	$123.94	6.494%	$131.9887	$131.99	$132.00	$132.00
Purchase #7	$72.62	7.783%	$78.272	$78.27	$78.25	$78.30
7 purchase totals =	$721.84		$765.0988	$765.10	$765.10	$765.10