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 $235.67   11.288%   $262.2724   $262.27   $262.25   $262.30  
  Purchase #2 $116.25   11.852%   $130.028   $130.03   $130.05   $130.00  
  Purchase #3 $88.26   5.164%   $92.8177   $92.82   $92.80   $92.80  
  Purchase #4 $36.42   7.260%   $39.0641   $39.06   $39.05   $39.10  
  Purchase #5 $227.78   8.535%   $247.221   $247.22   $247.20   $247.20  
  Purchase #6 $168.84   13.652%   $191.89   $191.89   $191.90   $191.90  
  Purchase #7 $221.80   7.555%   $238.557   $238.56   $238.55   $238.60  
  7 purchase totals = $1,095.02       $1,201.8502   $1,201.85   $1,201.80   $1,201.90