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 $72.48   3.143%   $74.758   $74.76   $74.75   $74.80  
  Purchase #2 $224.32   8.619%   $243.6541   $243.65   $243.65   $243.70  
  Purchase #3 $191.90   8.126%   $207.4938   $207.49   $207.50   $207.50  
  Purchase #4 $230.98   4.532%   $241.448   $241.45   $241.45   $241.40  
  Purchase #5 $118.28   13.842%   $134.6523   $134.65   $134.65   $134.70  
  Purchase #6 $73.99   4.299%   $77.1708   $77.17   $77.15   $77.20  
  Purchase #7 $80.27   9.490%   $87.8876   $87.89   $87.90   $87.90  
  7 purchase totals = $992.22       $1,067.0646   $1,067.06   $1,067.05   $1,067.20