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 $32.35   10.485%   $35.7419   $35.74   $35.75   $35.70  
  Purchase #2 $112.87   5.703%   $119.307   $119.31   $119.30   $119.30  
  Purchase #3 $236.79   7.798%   $255.2549   $255.25   $255.25   $255.30  
  Purchase #4 $151.65   5.123%   $159.419   $159.42   $159.40   $159.40  
  Purchase #5 $30.65   6.260%   $32.5687   $32.57   $32.55   $32.60  
  Purchase #6 $124.43   9.262%   $135.9547   $135.95   $135.95   $136.00  
  Purchase #7 $179.40   13.541%   $203.6926   $203.69   $203.70   $203.70  
  7 purchase totals = $868.14       $941.9388   $941.93   $941.90   $942.00