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	$140.69	12.654%	$158.4929	$158.49	$158.50	$158.50
Purchase #2	$215.43	4.404%	$224.9175	$224.92	$224.90	$224.90
Purchase #3	$218.37	3.343%	$225.6701	$225.67	$225.65	$225.70
Purchase #4	$135.57	4.269%	$141.3575	$141.36	$141.35	$141.40
Purchase #5	$136.66	11.103%	$151.8334	$151.83	$151.85	$151.80
Purchase #6	$60.69	5.272%	$63.8896	$63.89	$63.90	$63.90
Purchase #7	$98.79	13.719%	$112.343	$112.34	$112.35	$112.30
7 purchase totals =	$1,006.20		$1,078.5040	$1,078.50	$1,078.50	$1,078.50