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	$204.83	7.638%	$220.4749	$220.47	$220.45	$220.50
Purchase #2	$203.68	10.767%	$225.6102	$225.61	$225.60	$225.60
Purchase #3	$97.88	11.461%	$109.098	$109.10	$109.10	$109.10
Purchase #4	$141.41	3.835%	$146.8331	$146.83	$146.85	$146.80
Purchase #5	$212.37	12.428%	$238.7633	$238.76	$238.75	$238.80
Purchase #6	$196.96	5.741%	$208.2675	$208.27	$208.25	$208.30
Purchase #7	$61.41	8.285%	$66.4978	$66.50	$66.50	$66.50
7 purchase totals =	$1,118.54		$1,215.5448	$1,215.54	$1,215.50	$1,215.60