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	$184.50	8.342%	$199.891	$199.89	$199.90	$199.90
Purchase #2	$67.51	12.320%	$75.8272	$75.83	$75.85	$75.80
Purchase #3	$35.83	8.154%	$38.7516	$38.75	$38.75	$38.80
Purchase #4	$43.53	4.152%	$45.3374	$45.34	$45.35	$45.30
Purchase #5	$34.88	13.689%	$39.6547	$39.65	$39.65	$39.70
Purchase #6	$84.52	3.488%	$87.4681	$87.47	$87.45	$87.50
Purchase #7	$132.56	13.524%	$150.4874	$150.49	$150.50	$150.50
7 purchase totals =	$583.33		$637.4174	$637.42	$637.45	$637.50