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	$58.41	7.280%	$62.6622	$62.66	$62.65	$62.70
Purchase #2	$173.29	5.443%	$182.7222	$182.72	$182.70	$182.70
Purchase #3	$100.92	8.399%	$109.3963	$109.40	$109.40	$109.40
Purchase #4	$92.35	13.658%	$104.9632	$104.96	$104.95	$105.00
Purchase #5	$120.52	9.622%	$132.1164	$132.12	$132.10	$132.10
Purchase #6	$35.37	12.854%	$39.9165	$39.92	$39.90	$39.90
Purchase #7	$177.95	10.605%	$196.8216	$196.82	$196.80	$196.80
7 purchase totals =	$758.81		$828.5984	$828.60	$828.50	$828.60