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	$36.95	5.120%	$38.8418	$38.84	$38.85	$38.80
Purchase #2	$20.25	11.873%	$22.6543	$22.65	$22.65	$22.70
Purchase #3	$20.26	8.260%	$21.9335	$21.93	$21.95	$21.90
Purchase #4	$164.35	13.398%	$186.3696	$186.37	$186.35	$186.40
Purchase #5	$241.73	10.418%	$266.9134	$266.91	$266.90	$266.90
Purchase #6	$83.91	6.261%	$89.1636	$89.16	$89.15	$89.20
Purchase #7	$28.94	12.664%	$32.605	$32.61	$32.60	$32.60
7 purchase totals =	$596.39		$658.4812	$658.47	$658.45	$658.50