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 $82.56   13.823%   $93.9723   $93.97   $93.95   $94.00  
  Purchase #2 $51.65   9.361%   $56.485   $56.49   $56.50   $56.50  
  Purchase #3 $41.75   5.281%   $43.9548   $43.95   $43.95   $44.00  
  Purchase #4 $215.93   3.246%   $222.9391   $222.94   $222.95   $222.90  
  Purchase #5 $218.47   12.836%   $246.5128   $246.51   $246.50   $246.50  
  Purchase #6 $25.93   6.695%   $27.666   $27.67   $27.65   $27.70  
  Purchase #7 $26.62   10.260%   $29.3512   $29.35   $29.35   $29.40  
  7 purchase totals = $662.91       $720.8812   $720.88   $720.85   $721.00