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 $87.95   5.472%   $92.7626   $92.76   $92.75   $92.80  
  Purchase #2 $237.67   7.569%   $255.6592   $255.66   $255.65   $255.70  
  Purchase #3 $9.95   3.392%   $10.2875   $10.29   $10.30   $10.30  
  Purchase #4 $95.75   7.131%   $102.5779   $102.58   $102.60   $102.60  
  Purchase #5 $208.66   9.124%   $227.6981   $227.70   $227.70   $227.70  
  Purchase #6 $221.56   3.132%   $228.4993   $228.50   $228.50   $228.50  
  Purchase #7 $172.54   7.173%   $184.9163   $184.92   $184.90   $184.90  
  7 purchase totals = $1,034.08       $1,102.4009   $1,102.41   $1,102.40   $1,102.50