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	$173.57	11.124%	$192.8779	$192.88	$192.90	$192.90
Purchase #2	$102.51	8.747%	$111.4765	$111.48	$111.50	$111.50
Purchase #3	$108.50	8.642%	$117.8766	$117.88	$117.90	$117.90
Purchase #4	$163.48	4.783%	$171.2992	$171.30	$171.30	$171.30
Purchase #5	$176.85	3.412%	$182.8841	$182.88	$182.90	$182.90
Purchase #6	$235.47	9.357%	$257.5029	$257.50	$257.50	$257.50
Purchase #7	$84.51	12.533%	$95.1016	$95.10	$95.10	$95.10
7 purchase totals =	$1,044.89		$1,129.0188	$1,129.02	$1,129.10	$1,129.10