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	$147.69	4.212%	$153.9107	$153.91	$153.90	$153.90
Purchase #2	$78.37	12.147%	$87.8896	$87.89	$87.90	$87.90
Purchase #3	$123.41	7.197%	$132.2918	$132.29	$132.30	$132.30
Purchase #4	$103.78	9.554%	$113.6951	$113.70	$113.70	$113.70
Purchase #5	$133.73	4.419%	$139.6395	$139.64	$139.65	$139.60
Purchase #6	$20.33	7.268%	$21.8076	$21.81	$21.80	$21.80
Purchase #7	$122.33	13.846%	$139.2678	$139.27	$139.25	$139.30
7 purchase totals =	$729.64		$788.5021	$788.51	$788.50	$788.50