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	$240.82	5.720%	$254.5949	$254.59	$254.60	$254.60
Purchase #2	$65.28	10.442%	$72.0965	$72.10	$72.10	$72.10
Purchase #3	$85.32	7.375%	$91.6124	$91.61	$91.60	$91.60
Purchase #4	$168.81	6.513%	$179.8046	$179.80	$179.80	$179.80
Purchase #5	$182.52	4.709%	$191.1149	$191.11	$191.10	$191.10
Purchase #6	$102.48	9.826%	$112.5497	$112.55	$112.55	$112.50
Purchase #7	$30.54	11.420%	$34.0277	$34.03	$34.05	$34.00
7 purchase totals =	$875.77		$935.8007	$935.79	$935.80	$935.70