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 $22.96   5.636%   $24.254   $24.25   $24.25   $24.30  
  Purchase #2 $189.34   11.438%   $210.9967   $211.00   $211.00   $211.00  
  Purchase #3 $179.74   5.165%   $189.0236   $189.02   $189.00   $189.00  
  Purchase #4 $6.85   10.154%   $7.5455   $7.55   $7.55   $7.50  
  Purchase #5 $206.56   5.228%   $217.359   $217.36   $217.35   $217.40  
  Purchase #6 $131.65   9.324%   $143.925   $143.93   $143.95   $143.90  
  Purchase #7 $210.46   13.524%   $238.9226   $238.92   $238.90   $238.90  
  7 purchase totals = $947.56       $1,032.0264   $1,032.03   $1,032.00   $1,032.00