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 $216.26   3.862%   $224.612   $224.61   $224.60   $224.60  
  Purchase #2 $97.61   10.430%   $107.7907   $107.79   $107.80   $107.80  
  Purchase #3 $91.48   13.838%   $104.139   $104.14   $104.15   $104.10  
  Purchase #4 $167.55   5.383%   $176.5692   $176.57   $176.55   $176.60  
  Purchase #5 $246.93   8.701%   $268.4154   $268.42   $268.40   $268.40  
  Purchase #6 $63.98   13.246%   $72.4548   $72.45   $72.45   $72.50  
  Purchase #7 $76.60   5.465%   $80.7862   $80.79   $80.80   $80.80  
  7 purchase totals = $960.41       $1,034.7673   $1,034.77   $1,034.75   $1,034.80