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	$124.99	11.476%	$139.3339	$139.33	$139.35	$139.30
Purchase #2	$62.41	11.677%	$69.6976	$69.70	$69.70	$69.70
Purchase #3	$78.34	8.851%	$85.2739	$85.27	$85.25	$85.30
Purchase #4	$81.47	13.230%	$92.2485	$92.25	$92.25	$92.20
Purchase #5	$145.99	4.725%	$152.888	$152.89	$152.90	$152.90
Purchase #6	$9.80	3.257%	$10.1192	$10.12	$10.10	$10.10
Purchase #7	$69.40	4.315%	$72.3946	$72.39	$72.40	$72.40
7 purchase totals =	$572.40		$621.9557	$621.95	$621.95	$621.90