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	$125.53	10.132%	$138.2487	$138.25	$138.25	$138.20
Purchase #2	$13.52	9.477%	$14.8013	$14.80	$14.80	$14.80
Purchase #3	$182.32	7.801%	$196.5428	$196.54	$196.55	$196.50
Purchase #4	$84.50	10.461%	$93.3395	$93.34	$93.35	$93.30
Purchase #5	$172.62	13.768%	$196.3863	$196.39	$196.40	$196.40
Purchase #6	$161.38	3.169%	$166.4941	$166.49	$166.50	$166.50
Purchase #7	$225.60	12.737%	$254.3347	$254.33	$254.35	$254.30
7 purchase totals =	$965.47		$1,060.1474	$1,060.14	$1,060.20	$1,060.00