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 $181.89   10.782%   $201.5014   $201.50   $201.50   $201.50  
  Purchase #2 $156.57   13.194%   $177.2278   $177.23   $177.25   $177.20  
  Purchase #3 $147.48   4.606%   $154.2729   $154.27   $154.25   $154.30  
  Purchase #4 $85.78   7.147%   $91.9107   $91.91   $91.90   $91.90  
  Purchase #5 $217.79   9.219%   $237.8681   $237.87   $237.85   $237.90  
  Purchase #6 $239.43   9.484%   $262.1375   $262.14   $262.15   $262.10  
  Purchase #7 $113.38   7.265%   $121.6171   $121.62   $121.60   $121.60  
  7 purchase totals = $1,142.32       $1,246.5355   $1,246.54   $1,246.50   $1,246.50