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 $59.45   11.435%   $66.2481   $66.25   $66.25   $66.20  
  Purchase #2 $195.48   8.312%   $211.7283   $211.73   $211.75   $211.70  
  Purchase #3 $218.99   5.275%   $230.5417   $230.54   $230.55   $230.50  
  Purchase #4 $136.72   6.307%   $145.3429   $145.34   $145.35   $145.30  
  Purchase #5 $37.35   6.457%   $39.7617   $39.76   $39.75   $39.80  
  Purchase #6 $61.50   10.775%   $68.1266   $68.13   $68.15   $68.10  
  Purchase #7 $246.32   6.467%   $262.2495   $262.25   $262.25   $262.20  
  7 purchase totals = $955.81       $1,023.9988   $1,024.00   $1,024.05   $1,023.80