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 $201.98   11.518%   $225.2441   $225.24   $225.25   $225.20  
  Purchase #2 $174.49   10.677%   $193.1203   $193.12   $193.10   $193.10  
  Purchase #3 $147.43   5.646%   $155.7539   $155.75   $155.75   $155.80  
  Purchase #4 $234.88   4.110%   $244.5336   $244.53   $244.55   $244.50  
  Purchase #5 $131.26   7.471%   $141.0664   $141.07   $141.05   $141.10  
  Purchase #6 $63.80   9.357%   $69.7698   $69.77   $69.75   $69.80  
  Purchase #7 $73.89   3.772%   $76.6771   $76.68   $76.70   $76.70  
  7 purchase totals = $1,027.73       $1,106.1652   $1,106.16   $1,106.15   $1,106.20