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	$50.25	10.719%	$55.6363	$55.64	$55.65	$55.60
Purchase #2	$83.84	6.656%	$89.4204	$89.42	$89.40	$89.40
Purchase #3	$171.81	13.686%	$195.3239	$195.32	$195.30	$195.30
Purchase #4	$192.95	13.342%	$218.6934	$218.69	$218.70	$218.70
Purchase #5	$87.94	9.787%	$96.5467	$96.55	$96.55	$96.50
Purchase #6	$40.37	7.687%	$43.4732	$43.47	$43.45	$43.50
Purchase #7	$50.64	8.770%	$55.0811	$55.08	$55.10	$55.10
7 purchase totals =	$677.80		$754.1750	$754.17	$754.15	$754.10