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 $84.41   12.574%   $95.0237   $95.02   $95.00   $95.00  
  Purchase #2 $250.39   6.265%   $266.0769   $266.08   $266.10   $266.10  
  Purchase #3 $241.43   8.807%   $262.6927   $262.69   $262.70   $262.70  
  Purchase #4 $85.76   5.444%   $90.4288   $90.43   $90.45   $90.40  
  Purchase #5 $87.58   7.447%   $94.1021   $94.10   $94.10   $94.10  
  Purchase #6 $53.50   13.871%   $60.921   $60.92   $60.90   $60.90  
  Purchase #7 $175.65   13.270%   $198.9588   $198.96   $198.95   $199.00  
  7 purchase totals = $978.72       $1,068.2040   $1,068.20   $1,068.20   $1,068.20