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 $55.79   7.499%   $59.9737   $59.97   $59.95   $60.00  
  Purchase #2 $154.50   4.656%   $161.6935   $161.69   $161.70   $161.70  
  Purchase #3 $211.94   10.611%   $234.429   $234.43   $234.45   $234.40  
  Purchase #4 $213.37   6.621%   $227.4972   $227.50   $227.50   $227.50  
  Purchase #5 $204.57   11.236%   $227.5555   $227.56   $227.55   $227.60  
  Purchase #6 $177.56   10.624%   $196.424   $196.42   $196.40   $196.40  
  Purchase #7 $82.25   6.216%   $87.3627   $87.36   $87.35   $87.40  
  7 purchase totals = $1,099.98       $1,194.9356   $1,194.93   $1,194.90   $1,195.00