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	$93.65	5.193%	$98.5132	$98.51	$98.50	$98.50
Purchase #2	$65.59	3.362%	$67.7951	$67.80	$67.80	$67.80
Purchase #3	$219.78	3.676%	$227.8591	$227.86	$227.85	$227.90
Purchase #4	$214.84	12.572%	$241.8497	$241.85	$241.85	$241.80
Purchase #5	$112.33	3.221%	$115.9481	$115.95	$115.95	$115.90
Purchase #6	$71.54	3.509%	$74.0503	$74.05	$74.05	$74.10
Purchase #7	$172.85	11.382%	$192.5238	$192.52	$192.50	$192.50
7 purchase totals =	$950.58		$1,018.5393	$1,018.54	$1,018.50	$1,018.50