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 $33.62   3.312%   $34.7335   $34.73   $34.75   $34.70  
  Purchase #2 $55.32   10.617%   $61.1933   $61.19   $61.20   $61.20  
  Purchase #3 $41.83   13.432%   $47.4486   $47.45   $47.45   $47.40  
  Purchase #4 $119.60   3.775%   $124.1149   $124.11   $124.10   $124.10  
  Purchase #5 $77.40   10.151%   $85.2569   $85.26   $85.25   $85.30  
  Purchase #6 $240.74   12.443%   $270.6953   $270.70   $270.70   $270.70  
  Purchase #7 $83.89   8.684%   $91.175   $91.18   $91.20   $91.20  
  7 purchase totals = $652.40       $714.6175   $714.62   $714.65   $714.60