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 $56.81   10.755%   $62.9199   $62.92   $62.90   $62.90  
  Purchase #2 $240.84   13.705%   $273.8471   $273.85   $273.85   $273.80  
  Purchase #3 $93.69   3.435%   $96.9083   $96.91   $96.90   $96.90  
  Purchase #4 $222.99   6.747%   $238.0351   $238.04   $238.05   $238.00  
  Purchase #5 $164.77   7.826%   $177.6649   $177.66   $177.65   $177.70  
  Purchase #6 $124.65   8.232%   $134.9112   $134.91   $134.90   $134.90  
  Purchase #7 $196.27   6.744%   $209.5064   $209.51   $209.50   $209.50  
  7 purchase totals = $1,100.02       $1,193.7929   $1,193.80   $1,193.75   $1,193.70