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	$129.94	9.114%	$141.7827	$141.78	$141.80	$141.80
Purchase #2	$130.44	4.627%	$136.4755	$136.48	$136.50	$136.50
Purchase #3	$66.94	8.577%	$72.6814	$72.68	$72.70	$72.70
Purchase #4	$174.79	12.298%	$196.2857	$196.29	$196.30	$196.30
Purchase #5	$150.42	10.641%	$166.4262	$166.43	$166.45	$166.40
Purchase #6	$92.93	8.591%	$100.9136	$100.91	$100.90	$100.90
Purchase #7	$178.26	5.431%	$187.9413	$187.94	$187.95	$187.90
7 purchase totals =	$923.72		$1,002.5064	$1,002.51	$1,002.60	$1,002.50