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	$212.54	13.590%	$241.4242	$241.42	$241.40	$241.40
Purchase #2	$240.50	7.580%	$258.7299	$258.73	$258.75	$258.70
Purchase #3	$96.51	7.156%	$103.4163	$103.42	$103.40	$103.40
Purchase #4	$102.78	13.403%	$116.5556	$116.56	$116.55	$116.60
Purchase #5	$81.27	8.180%	$87.9179	$87.92	$87.90	$87.90
Purchase #6	$122.47	6.184%	$130.0435	$130.04	$130.05	$130.00
Purchase #7	$178.69	10.126%	$196.7841	$196.78	$196.80	$196.80
7 purchase totals =	$1,034.76		$1,134.8715	$1,134.87	$1,134.85	$1,134.80