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	$7.25	8.613%	$7.8744	$7.87	$7.85	$7.90
Purchase #2	$186.72	11.663%	$208.4972	$208.50	$208.50	$208.50
Purchase #3	$106.26	5.206%	$111.7919	$111.79	$111.80	$111.80
Purchase #4	$40.71	12.756%	$45.903	$45.90	$45.90	$45.90
Purchase #5	$102.51	6.312%	$108.9804	$108.98	$109.00	$109.00
Purchase #6	$75.91	13.862%	$86.4326	$86.43	$86.45	$86.40
Purchase #7	$205.33	4.710%	$215.001	$215.00	$215.00	$215.00
7 purchase totals =	$724.69		$784.4805	$784.47	$784.50	$784.50