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	$171.58	3.722%	$177.9662	$177.97	$177.95	$178.00
Purchase #2	$238.45	13.264%	$270.078	$270.08	$270.10	$270.10
Purchase #3	$140.28	8.699%	$152.483	$152.48	$152.50	$152.50
Purchase #4	$114.65	11.326%	$127.6353	$127.64	$127.65	$127.60
Purchase #5	$12.27	12.858%	$13.8477	$13.85	$13.85	$13.80
Purchase #6	$175.83	8.341%	$190.496	$190.50	$190.50	$190.50
Purchase #7	$208.54	12.531%	$234.6721	$234.67	$234.65	$234.70
7 purchase totals =	$1,061.60		$1,167.1783	$1,167.19	$1,167.20	$1,167.20