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	$43.60	12.389%	$49.0016	$49.00	$49.00	$49.00
Purchase #2	$36.52	12.791%	$41.1913	$41.19	$41.20	$41.20
Purchase #3	$202.58	9.704%	$222.2384	$222.24	$222.25	$222.20
Purchase #4	$148.50	8.768%	$161.5205	$161.52	$161.50	$161.50
Purchase #5	$127.34	3.301%	$131.5435	$131.54	$131.55	$131.50
Purchase #6	$205.82	12.439%	$231.4219	$231.42	$231.40	$231.40
Purchase #7	$164.58	9.311%	$179.904	$179.90	$179.90	$179.90
7 purchase totals =	$928.94		$1,016.8212	$1,016.81	$1,016.80	$1,016.70