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 $192.57   6.716%   $205.503   $205.50   $205.50   $205.50  
  Purchase #2 $60.59   4.161%   $63.1111   $63.11   $63.10   $63.10  
  Purchase #3 $25.43   4.438%   $26.5586   $26.56   $26.55   $26.60  
  Purchase #4 $157.80   8.580%   $171.3392   $171.34   $171.35   $171.30  
  Purchase #5 $204.33   6.616%   $217.8485   $217.85   $217.85   $217.80  
  Purchase #6 $163.50   8.615%   $177.5855   $177.59   $177.60   $177.60  
  Purchase #7 $213.97   8.158%   $231.4257   $231.43   $231.45   $231.40  
  7 purchase totals = $1,018.19       $1,093.3716   $1,093.38   $1,093.40   $1,093.30