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 $23.63   4.552%   $24.7056   $24.71   $24.70   $24.70  
  Purchase #2 $176.89   13.785%   $201.2743   $201.27   $201.25   $201.30  
  Purchase #3 $157.25   3.612%   $162.9299   $162.93   $162.95   $162.90  
  Purchase #4 $207.60   7.250%   $222.651   $222.65   $222.65   $222.70  
  Purchase #5 $153.35   12.688%   $172.807   $172.81   $172.80   $172.80  
  Purchase #6 $158.86   5.271%   $167.2335   $167.23   $167.25   $167.20  
  Purchase #7 $227.33   7.306%   $243.9387   $243.94   $243.95   $243.90  
  7 purchase totals = $1,104.91       $1,195.5400   $1,195.54   $1,195.55   $1,195.50