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 $93.66   9.512%   $102.5689   $102.57   $102.55   $102.60  
  Purchase #2 $52.30   4.566%   $54.688   $54.69   $54.70   $54.70  
  Purchase #3 $238.73   10.592%   $264.0163   $264.02   $264.00   $264.00  
  Purchase #4 $186.56   10.473%   $206.0984   $206.10   $206.10   $206.10  
  Purchase #5 $9.33   11.559%   $10.4085   $10.41   $10.40   $10.40  
  Purchase #6 $197.34   3.621%   $204.4857   $204.49   $204.50   $204.50  
  Purchase #7 $165.87   10.150%   $182.7058   $182.71   $182.70   $182.70  
  7 purchase totals = $943.79       $1,024.9716   $1,024.99   $1,024.95   $1,025.00