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 $126.71   6.218%   $134.5888   $134.59   $134.60   $134.60  
  Purchase #2 $176.45   11.810%   $197.2887   $197.29   $197.30   $197.30  
  Purchase #3 $10.42   7.213%   $11.1716   $11.17   $11.15   $11.20  
  Purchase #4 $141.46   7.860%   $152.5788   $152.58   $152.60   $152.60  
  Purchase #5 $49.77   8.696%   $54.098   $54.10   $54.10   $54.10  
  Purchase #6 $35.78   5.232%   $37.652   $37.65   $37.65   $37.70  
  Purchase #7 $182.36   12.525%   $205.2006   $205.20   $205.20   $205.20  
  7 purchase totals = $722.95       $792.5785   $792.58   $792.60   $792.70