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	$157.43	5.132%	$165.5093	$165.51	$165.50	$165.50
Purchase #2	$94.34	8.569%	$102.424	$102.42	$102.40	$102.40
Purchase #3	$115.33	10.526%	$127.4696	$127.47	$127.45	$127.50
Purchase #4	$59.88	11.772%	$66.9291	$66.93	$66.95	$66.90
Purchase #5	$76.55	13.286%	$86.7204	$86.72	$86.70	$86.70
Purchase #6	$131.69	10.742%	$145.8361	$145.84	$145.85	$145.80
Purchase #7	$196.36	10.302%	$216.589	$216.59	$216.60	$216.60
7 purchase totals =	$831.58		$911.4775	$911.48	$911.45	$911.40