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	$163.98	13.136%	$185.5204	$185.52	$185.50	$185.50
Purchase #2	$164.34	8.740%	$178.7033	$178.70	$178.70	$178.70
Purchase #3	$168.85	6.762%	$180.2676	$180.27	$180.25	$180.30
Purchase #4	$153.29	7.358%	$164.5691	$164.57	$164.55	$164.60
Purchase #5	$76.67	11.321%	$85.3498	$85.35	$85.35	$85.30
Purchase #6	$90.42	13.549%	$102.671	$102.67	$102.65	$102.70
Purchase #7	$238.72	7.602%	$256.8675	$256.87	$256.85	$256.90
7 purchase totals =	$1,056.27		$1,153.9487	$1,153.95	$1,153.85	$1,154.00