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	$215.79	9.472%	$236.2296	$236.23	$236.25	$236.20
Purchase #2	$167.77	6.719%	$179.0425	$179.04	$179.05	$179.00
Purchase #3	$114.47	11.247%	$127.3444	$127.34	$127.35	$127.30
Purchase #4	$163.57	12.698%	$184.3401	$184.34	$184.35	$184.30
Purchase #5	$143.51	13.258%	$162.5366	$162.54	$162.55	$162.50
Purchase #6	$82.32	6.342%	$87.5407	$87.54	$87.55	$87.50
Purchase #7	$91.72	8.516%	$99.5309	$99.53	$99.55	$99.50
7 purchase totals =	$979.15		$1,076.5648	$1,076.56	$1,076.65	$1,076.30