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 $58.44   8.816%   $63.5921   $63.59   $63.60   $63.60  
  Purchase #2 $231.87   4.247%   $241.7175   $241.72   $241.70   $241.70  
  Purchase #3 $190.70   7.754%   $205.4869   $205.49   $205.50   $205.50  
  Purchase #4 $93.70   6.352%   $99.6518   $99.65   $99.65   $99.70  
  Purchase #5 $218.92   11.620%   $244.3585   $244.36   $244.35   $244.40  
  Purchase #6 $158.99   10.471%   $175.6378   $175.64   $175.65   $175.60  
  Purchase #7 $154.71   12.540%   $174.1106   $174.11   $174.10   $174.10  
  7 purchase totals = $1,107.33       $1,204.5552   $1,204.56   $1,204.55   $1,204.60