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 $191.32   7.655%   $205.9655   $205.97   $205.95   $206.00  
  Purchase #2 $140.81   3.225%   $145.3511   $145.35   $145.35   $145.40  
  Purchase #3 $69.57   6.661%   $74.2041   $74.20   $74.20   $74.20  
  Purchase #4 $99.95   5.278%   $105.2254   $105.23   $105.25   $105.20  
  Purchase #5 $59.66   13.485%   $67.7052   $67.71   $67.70   $67.70  
  Purchase #6 $210.65   11.384%   $234.6304   $234.63   $234.65   $234.60  
  Purchase #7 $38.86   8.790%   $42.2758   $42.28   $42.30   $42.30  
  7 purchase totals = $810.82       $875.3575   $875.37   $875.40   $875.40