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 $157.66   5.734%   $166.7002   $166.70   $166.70   $166.70  
  Purchase #2 $227.77   5.857%   $241.1105   $241.11   $241.10   $241.10  
  Purchase #3 $33.59   6.556%   $35.7922   $35.79   $35.80   $35.80  
  Purchase #4 $177.53   10.546%   $196.2523   $196.25   $196.25   $196.30  
  Purchase #5 $213.40   9.244%   $233.1267   $233.13   $233.15   $233.10  
  Purchase #6 $139.29   7.330%   $149.5   $149.50   $149.50   $149.50  
  Purchase #7 $163.95   5.332%   $172.6918   $172.69   $172.70   $172.70  
  7 purchase totals = $1,113.19       $1,195.1737   $1,195.17   $1,195.20   $1,195.20