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	$151.59	5.514%	$159.9487	$159.95	$159.95	$159.90
Purchase #2	$39.83	9.183%	$43.4876	$43.49	$43.50	$43.50
Purchase #3	$233.46	10.674%	$258.3795	$258.38	$258.40	$258.40
Purchase #4	$34.88	4.602%	$36.4852	$36.49	$36.50	$36.50
Purchase #5	$190.50	3.496%	$197.1599	$197.16	$197.15	$197.20
Purchase #6	$35.96	12.747%	$40.5438	$40.54	$40.55	$40.50
Purchase #7	$139.39	3.600%	$144.408	$144.41	$144.40	$144.40
7 purchase totals =	$825.61		$880.4127	$880.42	$880.45	$880.40