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 $237.81   10.169%   $261.9929   $261.99   $262.00   $262.00  
  Purchase #2 $153.81   12.803%   $173.5023   $173.50   $173.50   $173.50  
  Purchase #3 $129.85   10.495%   $143.4778   $143.48   $143.50   $143.50  
  Purchase #4 $228.68   6.443%   $243.4139   $243.41   $243.40   $243.40  
  Purchase #5 $64.54   11.146%   $71.7336   $71.73   $71.75   $71.70  
  Purchase #6 $154.46   8.347%   $167.3528   $167.35   $167.35   $167.40  
  Purchase #7 $41.29   9.827%   $45.3476   $45.35   $45.35   $45.30  
  7 purchase totals = $1,010.44       $1,106.8209   $1,106.81   $1,106.85   $1,106.80