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 $95.73   7.529%   $102.9375   $102.94   $102.95   $102.90  
  Purchase #2 $215.49   5.664%   $227.6954   $227.70   $227.70   $227.70  
  Purchase #3 $66.32   7.257%   $71.1328   $71.13   $71.15   $71.10  
  Purchase #4 $238.72   6.157%   $253.418   $253.42   $253.40   $253.40  
  Purchase #5 $55.50   3.546%   $57.468   $57.47   $57.45   $57.50  
  Purchase #6 $224.37   9.639%   $245.997   $246.00   $246.00   $246.00  
  Purchase #7 $152.74   5.850%   $161.6753   $161.68   $161.70   $161.70  
  7 purchase totals = $1,048.87       $1,120.3240   $1,120.34   $1,120.35   $1,120.30