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	$114.64	10.569%	$126.7563	$126.76	$126.75	$126.80
Purchase #2	$90.97	3.482%	$94.1376	$94.14	$94.15	$94.10
Purchase #3	$133.71	7.736%	$144.0538	$144.05	$144.05	$144.10
Purchase #4	$50.94	10.558%	$56.3182	$56.32	$56.30	$56.30
Purchase #5	$90.31	6.685%	$96.3472	$96.35	$96.35	$96.30
Purchase #6	$88.30	13.276%	$100.0227	$100.02	$100.00	$100.00
Purchase #7	$10.94	9.106%	$11.9362	$11.94	$11.95	$11.90
7 purchase totals =	$579.81		$629.5720	$629.58	$629.55	$629.50