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	$203.35	6.626%	$216.824	$216.82	$216.80	$216.80
Purchase #2	$244.39	5.867%	$258.7284	$258.73	$258.75	$258.70
Purchase #3	$153.99	11.264%	$171.3354	$171.34	$171.35	$171.30
Purchase #4	$102.83	8.462%	$111.5315	$111.53	$111.55	$111.50
Purchase #5	$154.53	3.402%	$159.7871	$159.79	$159.80	$159.80
Purchase #6	$113.31	12.806%	$127.8205	$127.82	$127.80	$127.80
Purchase #7	$246.69	13.746%	$280.6	$280.60	$280.60	$280.60
7 purchase totals =	$1,219.09		$1,326.6269	$1,326.63	$1,326.65	$1,326.50