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 $213.94   10.629%   $236.6797   $236.68   $236.70   $236.70  
  Purchase #2 $233.55   10.810%   $258.7968   $258.80   $258.80   $258.80  
  Purchase #3 $179.91   12.853%   $203.0338   $203.03   $203.05   $203.00  
  Purchase #4 $243.49   5.415%   $256.675   $256.68   $256.70   $256.70  
  Purchase #5 $208.62   9.165%   $227.74   $227.74   $227.75   $227.70  
  Purchase #6 $153.73   11.774%   $171.8302   $171.83   $171.85   $171.80  
  Purchase #7 $133.35   5.472%   $140.6469   $140.65   $140.65   $140.60  
  7 purchase totals = $1,366.59       $1,495.4024   $1,495.41   $1,495.50   $1,495.30