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	$224.66	3.789%	$233.1724	$233.17	$233.15	$233.20
Purchase #2	$215.50	12.707%	$242.8836	$242.88	$242.90	$242.90
Purchase #3	$84.31	11.724%	$94.1945	$94.19	$94.20	$94.20
Purchase #4	$73.54	12.150%	$82.4751	$82.48	$82.50	$82.50
Purchase #5	$208.66	13.720%	$237.2882	$237.29	$237.30	$237.30
Purchase #6	$200.28	9.664%	$219.6351	$219.64	$219.65	$219.60
Purchase #7	$131.57	4.748%	$137.8169	$137.82	$137.80	$137.80
7 purchase totals =	$1,138.52		$1,247.4658	$1,247.47	$1,247.50	$1,247.50