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	$48.55	8.110%	$52.4874	$52.49	$52.50	$52.50
Purchase #2	$79.70	3.523%	$82.5078	$82.51	$82.50	$82.50
Purchase #3	$151.88	13.790%	$172.8243	$172.82	$172.80	$172.80
Purchase #4	$136.66	8.312%	$148.0192	$148.02	$148.00	$148.00
Purchase #5	$57.46	3.722%	$59.5987	$59.60	$59.60	$59.60
Purchase #6	$112.32	4.195%	$117.0318	$117.03	$117.05	$117.00
Purchase #7	$87.59	6.315%	$93.1213	$93.12	$93.10	$93.10
7 purchase totals =	$674.16		$725.5905	$725.59	$725.55	$725.50