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 $53.61   10.735%   $59.365   $59.37   $59.35   $59.40  
  Purchase #2 $246.46   5.844%   $260.8631   $260.86   $260.85   $260.90  
  Purchase #3 $49.95   13.592%   $56.7392   $56.74   $56.75   $56.70  
  Purchase #4 $203.39   12.370%   $228.5493   $228.55   $228.55   $228.50  
  Purchase #5 $175.88   8.610%   $191.0233   $191.02   $191.00   $191.00  
  Purchase #6 $211.41   13.365%   $239.6649   $239.66   $239.65   $239.70  
  Purchase #7 $220.54   5.345%   $232.3279   $232.33   $232.35   $232.30  
  7 purchase totals = $1,161.24       $1,268.5327   $1,268.53   $1,268.50   $1,268.50