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	$158.59	13.344%	$179.7522	$179.75	$179.75	$179.80
Purchase #2	$124.65	9.270%	$136.2051	$136.21	$136.20	$136.20
Purchase #3	$227.80	6.607%	$242.8507	$242.85	$242.85	$242.90
Purchase #4	$143.27	8.119%	$154.9021	$154.90	$154.90	$154.90
Purchase #5	$43.59	11.794%	$48.731	$48.73	$48.75	$48.70
Purchase #6	$63.55	13.297%	$72.0002	$72.00	$72.00	$72.00
Purchase #7	$186.36	6.510%	$198.492	$198.49	$198.50	$198.50
7 purchase totals =	$947.81		$1,032.9333	$1,032.93	$1,032.95	$1,033.00