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	$208.47	7.159%	$223.3944	$223.39	$223.40	$223.40
Purchase #2	$173.93	10.334%	$191.9039	$191.90	$191.90	$191.90
Purchase #3	$230.50	4.343%	$240.5106	$240.51	$240.50	$240.50
Purchase #4	$78.64	11.201%	$87.4485	$87.45	$87.45	$87.40
Purchase #5	$91.47	13.472%	$103.7928	$103.79	$103.80	$103.80
Purchase #6	$5.45	10.131%	$6.0021	$6.00	$6.00	$6.00
Purchase #7	$221.48	7.833%	$238.8285	$238.83	$238.85	$238.80
7 purchase totals =	$1,009.94		$1,091.8808	$1,091.87	$1,091.90	$1,091.80