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 $86.84   10.270%   $95.7585   $95.76   $95.75   $95.80  
  Purchase #2 $23.29   9.721%   $25.554   $25.55   $25.55   $25.60  
  Purchase #3 $94.99   3.450%   $98.2672   $98.27   $98.25   $98.30  
  Purchase #4 $62.39   9.346%   $68.221   $68.22   $68.20   $68.20  
  Purchase #5 $222.61   8.623%   $241.8057   $241.81   $241.80   $241.80  
  Purchase #6 $178.62   13.283%   $202.3461   $202.35   $202.35   $202.30  
  Purchase #7 $27.78   11.337%   $30.9294   $30.93   $30.95   $30.90  
  7 purchase totals = $696.52       $762.8819   $762.89   $762.85   $762.90