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	$11.67	5.244%	$12.282	$12.28	$12.30	$12.30
Purchase #2	$61.74	11.455%	$68.8123	$68.81	$68.80	$68.80
Purchase #3	$250.86	9.816%	$275.4844	$275.48	$275.50	$275.50
Purchase #4	$214.71	4.696%	$224.7928	$224.79	$224.80	$224.80
Purchase #5	$55.87	11.484%	$62.2861	$62.29	$62.30	$62.30
Purchase #6	$126.86	3.459%	$131.2481	$131.25	$131.25	$131.20
Purchase #7	$225.46	12.290%	$253.169	$253.17	$253.15	$253.20
7 purchase totals =	$947.17		$1,028.0747	$1,028.07	$1,028.10	$1,028.10