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 $230.34   7.495%   $247.604   $247.60   $247.60   $247.60  
  Purchase #2 $81.62   8.337%   $88.4247   $88.42   $88.40   $88.40  
  Purchase #3 $65.92   9.523%   $72.1976   $72.20   $72.20   $72.20  
  Purchase #4 $86.48   6.772%   $92.3364   $92.34   $92.35   $92.30  
  Purchase #5 $133.66   13.217%   $151.3258   $151.33   $151.35   $151.30  
  Purchase #6 $233.33   6.795%   $249.1848   $249.18   $249.20   $249.20  
  Purchase #7 $157.59   11.401%   $175.5568   $175.56   $175.55   $175.60  
  7 purchase totals = $988.94       $1,076.6301   $1,076.63   $1,076.65   $1,076.60