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	$200.94	7.274%	$215.5564	$215.56	$215.55	$215.60
Purchase #2	$103.92	9.493%	$113.7851	$113.79	$113.80	$113.80
Purchase #3	$224.56	11.715%	$250.8672	$250.87	$250.85	$250.90
Purchase #4	$210.95	13.685%	$239.8185	$239.82	$239.80	$239.80
Purchase #5	$184.46	13.646%	$209.6314	$209.63	$209.65	$209.60
Purchase #6	$90.57	13.207%	$102.5316	$102.53	$102.55	$102.50
Purchase #7	$86.83	5.198%	$91.3434	$91.34	$91.35	$91.30
7 purchase totals =	$1,102.23		$1,223.5336	$1,223.54	$1,223.55	$1,223.50