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 $90.29   4.769%   $94.5959   $94.60   $94.60   $94.60  
  Purchase #2 $150.83   9.240%   $164.7667   $164.77   $164.75   $164.80  
  Purchase #3 $135.38   8.436%   $146.8007   $146.80   $146.80   $146.80  
  Purchase #4 $171.66   12.595%   $193.2806   $193.28   $193.30   $193.30  
  Purchase #5 $74.76   4.251%   $77.938   $77.94   $77.95   $77.90  
  Purchase #6 $166.98   11.587%   $186.328   $186.33   $186.35   $186.30  
  Purchase #7 $238.56   3.610%   $247.172   $247.17   $247.15   $247.20  
  7 purchase totals = $1,028.46       $1,110.8819   $1,110.89   $1,110.90   $1,110.90