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	$136.66	11.173%	$151.929	$151.93	$151.95	$151.90
Purchase #2	$20.30	4.385%	$21.1902	$21.19	$21.20	$21.20
Purchase #3	$80.85	5.360%	$85.1836	$85.18	$85.20	$85.20
Purchase #4	$119.38	4.605%	$124.8774	$124.88	$124.90	$124.90
Purchase #5	$154.94	6.367%	$164.805	$164.81	$164.80	$164.80
Purchase #6	$159.62	10.573%	$176.4966	$176.50	$176.50	$176.50
Purchase #7	$117.25	6.565%	$124.9475	$124.95	$124.95	$124.90
7 purchase totals =	$789.00		$849.4293	$849.44	$849.50	$849.40