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 $216.36   11.861%   $242.0225   $242.02   $242.00   $242.00  
  Purchase #2 $191.49   8.832%   $208.4024   $208.40   $208.40   $208.40  
  Purchase #3 $97.26   8.616%   $105.6399   $105.64   $105.65   $105.60  
  Purchase #4 $210.71   11.270%   $234.457   $234.46   $234.45   $234.50  
  Purchase #5 $19.58   12.414%   $22.0107   $22.01   $22.00   $22.00  
  Purchase #6 $245.87   8.848%   $267.6246   $267.62   $267.60   $267.60  
  Purchase #7 $81.67   8.224%   $88.3865   $88.39   $88.40   $88.40  
  7 purchase totals = $1,062.94       $1,168.5436   $1,168.54   $1,168.50   $1,168.50