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	$43.67	13.380%	$49.513	$49.51	$49.50	$49.50
Purchase #2	$128.93	8.470%	$139.8504	$139.85	$139.85	$139.90
Purchase #3	$142.58	7.102%	$152.706	$152.71	$152.70	$152.70
Purchase #4	$56.53	5.222%	$59.482	$59.48	$59.50	$59.50
Purchase #5	$180.58	9.303%	$197.3794	$197.38	$197.40	$197.40
Purchase #6	$84.99	11.630%	$94.8743	$94.87	$94.85	$94.90
Purchase #7	$11.33	5.724%	$11.9785	$11.98	$12.00	$12.00
7 purchase totals =	$648.61		$705.7836	$705.78	$705.80	$705.90