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 $54.90   13.209%   $62.1517   $62.15   $62.15   $62.20  
  Purchase #2 $94.25   13.172%   $106.6646   $106.66   $106.65   $106.70  
  Purchase #3 $7.29   6.805%   $7.7861   $7.79   $7.80   $7.80  
  Purchase #4 $174.59   3.442%   $180.5994   $180.60   $180.60   $180.60  
  Purchase #5 $223.75   5.745%   $236.6044   $236.60   $236.60   $236.60  
  Purchase #6 $166.69   11.728%   $186.2394   $186.24   $186.25   $186.20  
  Purchase #7 $249.98   9.677%   $274.1706   $274.17   $274.15   $274.20  
  7 purchase totals = $971.45       $1,054.2162   $1,054.21   $1,054.20   $1,054.30