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	$99.72	13.846%	$113.5272	$113.53	$113.55	$113.50
Purchase #2	$178.43	7.132%	$191.1556	$191.16	$191.15	$191.20
Purchase #3	$81.53	13.296%	$92.3702	$92.37	$92.35	$92.40
Purchase #4	$194.69	5.823%	$206.0268	$206.03	$206.05	$206.00
Purchase #5	$62.96	13.849%	$71.6793	$71.68	$71.70	$71.70
Purchase #6	$208.28	4.396%	$217.436	$217.44	$217.45	$217.40
Purchase #7	$164.94	4.358%	$172.1281	$172.13	$172.15	$172.10
7 purchase totals =	$990.55		$1,064.3232	$1,064.34	$1,064.40	$1,064.30