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	$202.97	7.185%	$217.5534	$217.55	$217.55	$217.60
Purchase #2	$52.52	3.859%	$54.5467	$54.55	$54.55	$54.50
Purchase #3	$199.91	4.346%	$208.5981	$208.60	$208.60	$208.60
Purchase #4	$209.48	6.259%	$222.5914	$222.59	$222.60	$222.60
Purchase #5	$43.34	5.533%	$45.738	$45.74	$45.75	$45.70
Purchase #6	$203.53	9.181%	$222.2161	$222.22	$222.20	$222.20
Purchase #7	$113.25	5.214%	$119.1549	$119.15	$119.15	$119.20
7 purchase totals =	$1,025.00		$1,090.3986	$1,090.40	$1,090.40	$1,090.40