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	$30.62	4.535%	$32.0086	$32.01	$32.00	$32.00
Purchase #2	$182.97	4.138%	$190.5413	$190.54	$190.55	$190.50
Purchase #3	$86.30	6.601%	$91.9967	$92.00	$92.00	$92.00
Purchase #4	$199.67	8.553%	$216.7478	$216.75	$216.75	$216.70
Purchase #5	$145.58	5.201%	$153.1516	$153.15	$153.15	$153.20
Purchase #6	$169.63	9.574%	$185.8704	$185.87	$185.85	$185.90
Purchase #7	$132.99	6.696%	$141.895	$141.90	$141.90	$141.90
7 purchase totals =	$947.76		$1,012.2114	$1,012.22	$1,012.20	$1,012.20