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	$90.90	5.536%	$95.9322	$95.93	$95.95	$95.90
Purchase #2	$215.39	13.507%	$244.4827	$244.48	$244.50	$244.50
Purchase #3	$90.48	12.709%	$101.9791	$101.98	$102.00	$102.00
Purchase #4	$85.68	13.360%	$97.1268	$97.13	$97.15	$97.10
Purchase #5	$241.43	6.393%	$256.8646	$256.86	$256.85	$256.90
Purchase #6	$86.78	6.716%	$92.6081	$92.61	$92.60	$92.60
Purchase #7	$191.56	3.538%	$198.3374	$198.34	$198.35	$198.30
7 purchase totals =	$1,002.22		$1,087.3309	$1,087.33	$1,087.40	$1,087.30