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	$131.81	10.782%	$146.0218	$146.02	$146.00	$146.00
Purchase #2	$108.39	13.807%	$123.3554	$123.36	$123.35	$123.40
Purchase #3	$119.78	12.190%	$134.3812	$134.38	$134.40	$134.40
Purchase #4	$136.42	8.757%	$148.3663	$148.37	$148.35	$148.40
Purchase #5	$173.56	13.588%	$197.1433	$197.14	$197.15	$197.10
Purchase #6	$32.54	12.544%	$36.6218	$36.62	$36.60	$36.60
Purchase #7	$213.42	9.336%	$233.3449	$233.34	$233.35	$233.30
7 purchase totals =	$915.92		$1,019.2347	$1,019.23	$1,019.20	$1,019.20