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	$94.63	8.508%	$102.6811	$102.68	$102.70	$102.70
Purchase #2	$25.58	11.698%	$28.5723	$28.57	$28.55	$28.60
Purchase #3	$91.75	3.687%	$95.1328	$95.13	$95.15	$95.10
Purchase #4	$121.57	4.620%	$127.1865	$127.19	$127.20	$127.20
Purchase #5	$65.55	11.279%	$72.9434	$72.94	$72.95	$72.90
Purchase #6	$208.94	9.356%	$228.4884	$228.49	$228.50	$228.50
Purchase #7	$97.79	5.189%	$102.8643	$102.86	$102.85	$102.90
7 purchase totals =	$705.81		$757.8688	$757.86	$757.90	$757.90