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 $65.53   5.271%   $68.9841   $68.98   $69.00   $69.00  
  Purchase #2 $148.65   8.103%   $160.6951   $160.70   $160.70   $160.70  
  Purchase #3 $206.50   9.413%   $225.9378   $225.94   $225.95   $225.90  
  Purchase #4 $129.66   12.522%   $145.896   $145.90   $145.90   $145.90  
  Purchase #5 $196.26   4.262%   $204.6246   $204.62   $204.60   $204.60  
  Purchase #6 $143.90   7.640%   $154.894   $154.89   $154.90   $154.90  
  Purchase #7 $56.51   11.628%   $63.081   $63.08   $63.10   $63.10  
  7 purchase totals = $947.01       $1,024.1126   $1,024.11   $1,024.15   $1,024.10