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	$108.94	4.212%	$113.5286	$113.53	$113.55	$113.50
Purchase #2	$167.26	7.579%	$179.9366	$179.94	$179.95	$179.90
Purchase #3	$153.89	11.811%	$172.0659	$172.07	$172.05	$172.10
Purchase #4	$215.39	13.537%	$244.5473	$244.55	$244.55	$244.50
Purchase #5	$89.28	10.192%	$98.3794	$98.38	$98.40	$98.40
Purchase #6	$153.77	9.531%	$168.4258	$168.43	$168.45	$168.40
Purchase #7	$237.80	3.648%	$246.4749	$246.47	$246.45	$246.50
7 purchase totals =	$1,126.33		$1,223.3585	$1,223.37	$1,223.40	$1,223.30