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 $61.81   9.715%   $67.8148   $67.81   $67.80   $67.80  
  Purchase #2 $104.54   10.672%   $115.6965   $115.70   $115.70   $115.70  
  Purchase #3 $165.43   5.867%   $175.1358   $175.14   $175.15   $175.10  
  Purchase #4 $217.71   6.452%   $231.7566   $231.76   $231.75   $231.80  
  Purchase #5 $250.62   12.633%   $282.2808   $282.28   $282.30   $282.30  
  Purchase #6 $221.70   5.474%   $233.8359   $233.84   $233.85   $233.80  
  Purchase #7 $211.83   10.813%   $234.7352   $234.74   $234.75   $234.70  
  7 purchase totals = $1,233.64       $1,341.2556   $1,341.27   $1,341.30   $1,341.20