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 $58.52   3.192%   $60.388   $60.39   $60.40   $60.40  
  Purchase #2 $249.72   4.386%   $260.6727   $260.67   $260.65   $260.70  
  Purchase #3 $125.25   5.362%   $131.9659   $131.97   $131.95   $132.00  
  Purchase #4 $246.63   12.172%   $276.6498   $276.65   $276.65   $276.60  
  Purchase #5 $9.99   11.821%   $11.1709   $11.17   $11.15   $11.20  
  Purchase #6 $241.71   3.820%   $250.9433   $250.94   $250.95   $250.90  
  Purchase #7 $93.79   10.704%   $103.8293   $103.83   $103.85   $103.80  
  7 purchase totals = $1,025.61       $1,095.6199   $1,095.62   $1,095.60   $1,095.60