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	$86.62	4.216%	$90.2719	$90.27	$90.25	$90.30
Purchase #2	$196.27	12.438%	$220.6821	$220.68	$220.70	$220.70
Purchase #3	$197.30	5.716%	$208.5777	$208.58	$208.60	$208.60
Purchase #4	$37.87	13.350%	$42.9256	$42.93	$42.95	$42.90
Purchase #5	$19.96	3.462%	$20.651	$20.65	$20.65	$20.70
Purchase #6	$155.43	7.766%	$167.5007	$167.50	$167.50	$167.50
Purchase #7	$128.59	12.585%	$144.7731	$144.77	$144.75	$144.80
7 purchase totals =	$822.04		$895.3821	$895.38	$895.40	$895.50