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 $71.46   5.493%   $75.3853   $75.39   $75.40   $75.40  
  Purchase #2 $176.49   11.487%   $196.7634   $196.76   $196.75   $196.80  
  Purchase #3 $159.99   11.168%   $177.8577   $177.86   $177.85   $177.90  
  Purchase #4 $232.85   12.493%   $261.94   $261.94   $261.95   $261.90  
  Purchase #5 $123.86   5.662%   $130.873   $130.87   $130.85   $130.90  
  Purchase #6 $204.90   12.316%   $230.1355   $230.14   $230.15   $230.10  
  Purchase #7 $211.56   7.679%   $227.8057   $227.81   $227.80   $227.80  
  7 purchase totals = $1,181.11       $1,300.7606   $1,300.77   $1,300.75   $1,300.80