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 $179.30   12.635%   $201.9546   $201.95   $201.95   $202.00  
  Purchase #2 $60.39   4.320%   $62.9988   $63.00   $63.00   $63.00  
  Purchase #3 $153.77   8.424%   $166.7236   $166.72   $166.70   $166.70  
  Purchase #4 $157.69   13.282%   $178.6344   $178.63   $178.65   $178.60  
  Purchase #5 $64.99   3.789%   $67.4525   $67.45   $67.45   $67.50  
  Purchase #6 $246.49   7.266%   $264.4   $264.40   $264.40   $264.40  
  Purchase #7 $192.66   13.568%   $218.8001   $218.80   $218.80   $218.80  
  7 purchase totals = $1,055.29       $1,160.9640   $1,160.95   $1,160.95   $1,161.00