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	$231.28	3.472%	$239.31	$239.31	$239.30	$239.30
Purchase #2	$146.65	9.705%	$160.8824	$160.88	$160.90	$160.90
Purchase #3	$82.84	7.514%	$89.0646	$89.06	$89.05	$89.10
Purchase #4	$225.46	7.273%	$241.8577	$241.86	$241.85	$241.90
Purchase #5	$137.49	4.367%	$143.4942	$143.49	$143.50	$143.50
Purchase #6	$166.39	7.600%	$179.0356	$179.04	$179.05	$179.00
Purchase #7	$8.43	5.864%	$8.9243	$8.92	$8.90	$8.90
7 purchase totals =	$998.54		$1,062.5688	$1,062.56	$1,062.55	$1,062.60