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	$148.92	13.414%	$168.8961	$168.90	$168.90	$168.90
Purchase #2	$87.69	7.643%	$94.3921	$94.39	$94.40	$94.40
Purchase #3	$172.35	12.222%	$193.4146	$193.41	$193.40	$193.40
Purchase #4	$206.86	5.276%	$217.7739	$217.77	$217.75	$217.80
Purchase #5	$242.75	12.676%	$273.521	$273.52	$273.50	$273.50
Purchase #6	$213.64	13.222%	$241.8875	$241.89	$241.90	$241.90
Purchase #7	$35.56	10.709%	$39.3681	$39.37	$39.35	$39.40
7 purchase totals =	$1,107.77		$1,229.2533	$1,229.25	$1,229.20	$1,229.30