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	$229.83	4.189%	$239.4576	$239.46	$239.45	$239.50
Purchase #2	$246.63	7.241%	$264.4885	$264.49	$264.50	$264.50
Purchase #3	$177.25	8.622%	$192.5325	$192.53	$192.55	$192.50
Purchase #4	$43.88	4.614%	$45.9046	$45.90	$45.90	$45.90
Purchase #5	$188.89	3.810%	$196.0867	$196.09	$196.10	$196.10
Purchase #6	$117.33	12.868%	$132.428	$132.43	$132.45	$132.40
Purchase #7	$59.31	11.486%	$66.1223	$66.12	$66.10	$66.10
7 purchase totals =	$1,063.12		$1,137.0202	$1,137.02	$1,137.05	$1,137.00