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	$197.46	8.444%	$214.1335	$214.13	$214.15	$214.10
Purchase #2	$215.98	9.466%	$236.4247	$236.42	$236.40	$236.40
Purchase #3	$187.87	13.620%	$213.4579	$213.46	$213.45	$213.50
Purchase #4	$239.92	6.758%	$256.1338	$256.13	$256.15	$256.10
Purchase #5	$55.73	13.164%	$63.0663	$63.07	$63.05	$63.10
Purchase #6	$84.35	7.232%	$90.4502	$90.45	$90.45	$90.50
Purchase #7	$84.62	5.317%	$89.1192	$89.12	$89.10	$89.10
7 purchase totals =	$1,065.93		$1,162.7856	$1,162.78	$1,162.75	$1,162.80