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 $118.84   5.454%   $125.3215   $125.32   $125.30   $125.30  
  Purchase #2 $53.40   7.652%   $57.4862   $57.49   $57.50   $57.50  
  Purchase #3 $247.92   8.389%   $268.718   $268.72   $268.70   $268.70  
  Purchase #4 $221.32   12.185%   $248.2878   $248.29   $248.30   $248.30  
  Purchase #5 $26.42   10.772%   $29.266   $29.27   $29.25   $29.30  
  Purchase #6 $239.93   12.266%   $269.3598   $269.36   $269.35   $269.40  
  Purchase #7 $156.93   13.280%   $177.7703   $177.77   $177.75   $177.80  
  7 purchase totals = $1,064.76       $1,176.2096   $1,176.22   $1,176.15   $1,176.30