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	$122.55	13.862%	$139.5379	$139.54	$139.55	$139.50
Purchase #2	$220.98	4.805%	$231.5981	$231.60	$231.60	$231.60
Purchase #3	$50.69	5.636%	$53.5469	$53.55	$53.55	$53.50
Purchase #4	$48.88	13.263%	$55.363	$55.36	$55.35	$55.40
Purchase #5	$201.36	13.454%	$228.451	$228.45	$228.45	$228.50
Purchase #6	$146.91	12.213%	$164.8521	$164.85	$164.85	$164.90
Purchase #7	$166.48	7.866%	$179.5753	$179.58	$179.60	$179.60
7 purchase totals =	$957.85		$1,052.9243	$1,052.93	$1,052.95	$1,053.00