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	$82.42	5.411%	$86.8797	$86.88	$86.90	$86.90
Purchase #2	$80.25	8.723%	$87.2502	$87.25	$87.25	$87.30
Purchase #3	$152.76	6.593%	$162.8315	$162.83	$162.85	$162.80
Purchase #4	$198.60	8.642%	$215.763	$215.76	$215.75	$215.80
Purchase #5	$27.34	9.368%	$29.9012	$29.90	$29.90	$29.90
Purchase #6	$98.60	12.850%	$111.2701	$111.27	$111.25	$111.30
Purchase #7	$92.35	11.151%	$102.6479	$102.65	$102.65	$102.60
7 purchase totals =	$732.32		$796.5436	$796.54	$796.55	$796.60