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 $54.59   13.454%   $61.9345   $61.93   $61.95   $61.90  
  Purchase #2 $208.81   12.620%   $235.1618   $235.16   $235.15   $235.20  
  Purchase #3 $248.98   5.355%   $262.3129   $262.31   $262.30   $262.30  
  Purchase #4 $195.51   8.312%   $211.7608   $211.76   $211.75   $211.80  
  Purchase #5 $229.53   6.685%   $244.8741   $244.87   $244.85   $244.90  
  Purchase #6 $100.39   4.443%   $104.8503   $104.85   $104.85   $104.90  
  Purchase #7 $56.33   8.180%   $60.9378   $60.94   $60.95   $60.90  
  7 purchase totals = $1,094.14       $1,181.8322   $1,181.82   $1,181.80   $1,181.90