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 $216.88   9.264%   $236.9718   $236.97   $236.95   $237.00  
  Purchase #2 $130.94   7.770%   $141.114   $141.11   $141.10   $141.10  
  Purchase #3 $71.89   12.635%   $80.9733   $80.97   $80.95   $81.00  
  Purchase #4 $145.82   9.736%   $160.017   $160.02   $160.00   $160.00  
  Purchase #5 $74.64   5.406%   $78.675   $78.68   $78.70   $78.70  
  Purchase #6 $112.72   5.546%   $118.9715   $118.97   $118.95   $119.00  
  Purchase #7 $224.66   8.610%   $244.0032   $244.00   $244.00   $244.00  
  7 purchase totals = $977.55       $1,060.7258   $1,060.72   $1,060.65   $1,060.80