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	$72.46	13.850%	$82.4957	$82.50	$82.50	$82.50
Purchase #2	$202.47	12.733%	$228.2505	$228.25	$228.25	$228.30
Purchase #3	$243.31	12.862%	$274.6045	$274.60	$274.60	$274.60
Purchase #4	$102.68	9.134%	$112.0588	$112.06	$112.05	$112.10
Purchase #5	$136.64	3.238%	$141.0644	$141.06	$141.05	$141.10
Purchase #6	$150.27	8.158%	$162.529	$162.53	$162.55	$162.50
Purchase #7	$13.51	7.777%	$14.5607	$14.56	$14.55	$14.60
7 purchase totals =	$921.34		$1,015.5636	$1,015.56	$1,015.55	$1,015.70