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	$184.94	4.301%	$192.8943	$192.89	$192.90	$192.90
Purchase #2	$50.37	6.874%	$53.8324	$53.83	$53.85	$53.80
Purchase #3	$125.32	10.396%	$138.3483	$138.35	$138.35	$138.30
Purchase #4	$80.90	13.162%	$91.5481	$91.55	$91.55	$91.50
Purchase #5	$114.48	8.120%	$123.7758	$123.78	$123.80	$123.80
Purchase #6	$60.63	5.223%	$63.7967	$63.80	$63.80	$63.80
Purchase #7	$78.50	13.227%	$88.8832	$88.88	$88.90	$88.90
7 purchase totals =	$695.14		$753.0788	$753.08	$753.15	$753.00