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	$149.86	4.180%	$156.1241	$156.12	$156.10	$156.10
Purchase #2	$112.74	4.255%	$117.5371	$117.54	$117.55	$117.50
Purchase #3	$59.41	12.206%	$66.6616	$66.66	$66.65	$66.70
Purchase #4	$168.57	12.724%	$190.0188	$190.02	$190.00	$190.00
Purchase #5	$33.67	10.491%	$37.2023	$37.20	$37.20	$37.20
Purchase #6	$135.93	10.718%	$150.499	$150.50	$150.50	$150.50
Purchase #7	$24.88	10.659%	$27.532	$27.53	$27.55	$27.50
7 purchase totals =	$685.06		$745.5749	$745.57	$745.55	$745.50