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 $184.99   6.644%   $197.2807   $197.28   $197.30   $197.30  
  Purchase #2 $96.99   12.326%   $108.945   $108.95   $108.95   $108.90  
  Purchase #3 $51.54   9.519%   $56.4461   $56.45   $56.45   $56.40  
  Purchase #4 $130.62   3.514%   $135.21   $135.21   $135.20   $135.20  
  Purchase #5 $138.63   13.833%   $157.8067   $157.81   $157.80   $157.80  
  Purchase #6 $197.51   4.326%   $206.0543   $206.05   $206.05   $206.10  
  Purchase #7 $222.97   10.294%   $245.9225   $245.92   $245.90   $245.90  
  7 purchase totals = $1,023.25       $1,107.6653   $1,107.67   $1,107.65   $1,107.60