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 $182.48   13.745%   $207.5619   $207.56   $207.55   $207.60  
  Purchase #2 $181.88   10.111%   $200.2699   $200.27   $200.25   $200.30  
  Purchase #3 $158.99   3.749%   $164.9505   $164.95   $164.95   $165.00  
  Purchase #4 $148.32   8.496%   $160.9213   $160.92   $160.90   $160.90  
  Purchase #5 $13.94   3.815%   $14.4718   $14.47   $14.45   $14.50  
  Purchase #6 $41.75   13.345%   $47.3215   $47.32   $47.30   $47.30  
  Purchase #7 $247.82   5.206%   $260.7215   $260.72   $260.70   $260.70  
  7 purchase totals = $975.18       $1,056.2184   $1,056.21   $1,056.10   $1,056.30