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 $177.69   13.621%   $201.8932   $201.89   $201.90   $201.90  
  Purchase #2 $92.34   3.484%   $95.5571   $95.56   $95.55   $95.60  
  Purchase #3 $184.96   10.270%   $203.9554   $203.96   $203.95   $204.00  
  Purchase #4 $208.68   13.863%   $237.6093   $237.61   $237.60   $237.60  
  Purchase #5 $206.28   3.169%   $212.817   $212.82   $212.80   $212.80  
  Purchase #6 $175.39   6.447%   $186.6974   $186.70   $186.70   $186.70  
  Purchase #7 $202.93   6.865%   $216.8611   $216.86   $216.85   $216.90  
  7 purchase totals = $1,248.27       $1,355.3905   $1,355.40   $1,355.35   $1,355.50