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 $242.95   7.178%   $260.389   $260.39   $260.40   $260.40  
  Purchase #2 $88.88   11.527%   $99.1252   $99.13   $99.15   $99.10  
  Purchase #3 $22.44   12.850%   $25.3235   $25.32   $25.30   $25.30  
  Purchase #4 $55.69   8.520%   $60.4348   $60.43   $60.45   $60.40  
  Purchase #5 $192.39   5.112%   $202.225   $202.23   $202.25   $202.20  
  Purchase #6 $225.31   5.675%   $238.0963   $238.10   $238.10   $238.10  
  Purchase #7 $185.87   12.445%   $209.0015   $209.00   $209.00   $209.00  
  7 purchase totals = $1,013.53       $1,094.5953   $1,094.60   $1,094.65   $1,094.50