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	$65.83	9.640%	$72.176	$72.18	$72.20	$72.20
Purchase #2	$93.57	10.619%	$103.5062	$103.51	$103.50	$103.50
Purchase #3	$117.44	5.276%	$123.6361	$123.64	$123.65	$123.60
Purchase #4	$238.54	4.192%	$248.5396	$248.54	$248.55	$248.50
Purchase #5	$211.71	3.380%	$218.8658	$218.87	$218.85	$218.90
Purchase #6	$231.69	10.824%	$256.7681	$256.77	$256.75	$256.80
Purchase #7	$140.96	10.421%	$155.6494	$155.65	$155.65	$155.60
7 purchase totals =	$1,099.74		$1,179.1412	$1,179.16	$1,179.15	$1,179.10