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	$150.59	9.211%	$164.4608	$164.46	$164.45	$164.50
Purchase #2	$198.78	9.559%	$217.7814	$217.78	$217.80	$217.80
Purchase #3	$180.81	8.842%	$196.7972	$196.80	$196.80	$196.80
Purchase #4	$99.56	10.849%	$110.3613	$110.36	$110.35	$110.40
Purchase #5	$60.78	8.599%	$66.0065	$66.01	$66.00	$66.00
Purchase #6	$205.81	5.171%	$216.4524	$216.45	$216.45	$216.50
Purchase #7	$118.53	4.256%	$123.5746	$123.57	$123.55	$123.60
7 purchase totals =	$1,014.86		$1,095.4342	$1,095.43	$1,095.40	$1,095.60