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 $59.54   8.725%   $64.7349   $64.73   $64.75   $64.70  
  Purchase #2 $205.93   8.121%   $222.6536   $222.65   $222.65   $222.70  
  Purchase #3 $214.81   8.547%   $233.1698   $233.17   $233.15   $233.20  
  Purchase #4 $98.40   7.145%   $105.4307   $105.43   $105.45   $105.40  
  Purchase #5 $12.86   6.415%   $13.685   $13.69   $13.70   $13.70  
  Purchase #6 $212.29   6.495%   $226.0782   $226.08   $226.10   $226.10  
  Purchase #7 $58.71   8.466%   $63.6804   $63.68   $63.70   $63.70  
  7 purchase totals = $862.54       $929.4326   $929.43   $929.50   $929.50