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 $119.76   5.382%   $126.2055   $126.21   $126.20   $126.20  
  Purchase #2 $97.59   7.347%   $104.7599   $104.76   $104.75   $104.80  
  Purchase #3 $221.33   3.356%   $228.7578   $228.76   $228.75   $228.80  
  Purchase #4 $224.87   7.221%   $241.1079   $241.11   $241.10   $241.10  
  Purchase #5 $169.30   6.282%   $179.9354   $179.94   $179.95   $179.90  
  Purchase #6 $135.76   3.319%   $140.2659   $140.27   $140.25   $140.30  
  Purchase #7 $108.71   13.340%   $123.2119   $123.21   $123.20   $123.20  
  7 purchase totals = $1,077.32       $1,144.2443   $1,144.26   $1,144.20   $1,144.30