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	$78.83	4.831%	$82.6383	$82.64	$82.65	$82.60
Purchase #2	$236.47	10.725%	$261.8314	$261.83	$261.85	$261.80
Purchase #3	$27.66	13.702%	$31.45	$31.45	$31.45	$31.50
Purchase #4	$242.25	10.674%	$268.1078	$268.11	$268.10	$268.10
Purchase #5	$109.82	7.791%	$118.3761	$118.38	$118.40	$118.40
Purchase #6	$148.52	3.376%	$153.534	$153.53	$153.55	$153.50
Purchase #7	$227.58	8.470%	$246.856	$246.86	$246.85	$246.90
7 purchase totals =	$1,071.13		$1,162.7936	$1,162.80	$1,162.85	$1,162.80