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	$111.54	5.245%	$117.3903	$117.39	$117.40	$117.40
Purchase #2	$41.51	4.480%	$43.3696	$43.37	$43.35	$43.40
Purchase #3	$229.45	11.576%	$256.0111	$256.01	$256.00	$256.00
Purchase #4	$232.42	7.576%	$250.0281	$250.03	$250.05	$250.00
Purchase #5	$111.59	3.555%	$115.557	$115.56	$115.55	$115.60
Purchase #6	$189.69	10.127%	$208.8999	$208.90	$208.90	$208.90
Purchase #7	$212.69	8.868%	$231.5513	$231.55	$231.55	$231.60
7 purchase totals =	$1,128.89		$1,222.8073	$1,222.81	$1,222.80	$1,222.90