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 $208.58   7.406%   $224.0274   $224.03   $224.05   $224.00  
  Purchase #2 $22.68   7.585%   $24.4003   $24.40   $24.40   $24.40  
  Purchase #3 $184.89   12.622%   $208.2268   $208.23   $208.25   $208.20  
  Purchase #4 $231.48   13.372%   $262.4335   $262.43   $262.45   $262.40  
  Purchase #5 $89.33   6.691%   $95.3071   $95.31   $95.30   $95.30  
  Purchase #6 $87.36   5.511%   $92.1744   $92.17   $92.15   $92.20  
  Purchase #7 $165.33   13.740%   $188.0463   $188.05   $188.05   $188.00  
  7 purchase totals = $989.65       $1,094.6158   $1,094.62   $1,094.65   $1,094.50