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	$99.70	13.431%	$113.0907	$113.09	$113.10	$113.10
Purchase #2	$88.61	6.569%	$94.4308	$94.43	$94.45	$94.40
Purchase #3	$198.29	6.826%	$211.8253	$211.83	$211.85	$211.80
Purchase #4	$82.28	4.548%	$86.0221	$86.02	$86.00	$86.00
Purchase #5	$185.89	3.755%	$192.8702	$192.87	$192.85	$192.90
Purchase #6	$129.85	5.421%	$136.8892	$136.89	$136.90	$136.90
Purchase #7	$162.75	4.554%	$170.1616	$170.16	$170.15	$170.20
7 purchase totals =	$947.37		$1,005.2899	$1,005.29	$1,005.30	$1,005.30