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	$60.67	5.493%	$64.0026	$64.00	$64.00	$64.00
Purchase #2	$38.58	12.667%	$43.4669	$43.47	$43.45	$43.50
Purchase #3	$82.32	10.334%	$90.8269	$90.83	$90.85	$90.80
Purchase #4	$156.79	11.834%	$175.3445	$175.34	$175.35	$175.30
Purchase #5	$135.93	7.606%	$146.2688	$146.27	$146.25	$146.30
Purchase #6	$25.51	8.851%	$27.7679	$27.77	$27.75	$27.80
Purchase #7	$194.35	9.799%	$213.3944	$213.39	$213.40	$213.40
7 purchase totals =	$694.15		$761.0720	$761.07	$761.05	$761.10