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	$199.61	6.471%	$212.5268	$212.53	$212.55	$212.50
Purchase #2	$97.39	6.695%	$103.9103	$103.91	$103.90	$103.90
Purchase #3	$49.61	13.462%	$56.2885	$56.29	$56.30	$56.30
Purchase #4	$123.29	6.719%	$131.5739	$131.57	$131.55	$131.60
Purchase #5	$249.48	6.678%	$266.1403	$266.14	$266.15	$266.10
Purchase #6	$13.41	3.798%	$13.9193	$13.92	$13.90	$13.90
Purchase #7	$234.54	9.159%	$256.0215	$256.02	$256.00	$256.00
7 purchase totals =	$967.33		$1,040.3806	$1,040.38	$1,040.35	$1,040.30