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 $93.95   12.501%   $105.6947   $105.69   $105.70   $105.70  
  Purchase #2 $197.70   4.586%   $206.7665   $206.77   $206.75   $206.80  
  Purchase #3 $73.77   4.692%   $77.2313   $77.23   $77.25   $77.20  
  Purchase #4 $80.59   8.810%   $87.69   $87.69   $87.70   $87.70  
  Purchase #5 $131.58   7.470%   $141.409   $141.41   $141.40   $141.40  
  Purchase #6 $117.69   12.112%   $131.9446   $131.94   $131.95   $131.90  
  Purchase #7 $229.67   6.643%   $244.927   $244.93   $244.95   $244.90  
  7 purchase totals = $924.95       $995.6631   $995.66   $995.70   $995.60