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 $168.54   11.670%   $188.2086   $188.21   $188.20   $188.20  
  Purchase #2 $242.53   3.353%   $250.662   $250.66   $250.65   $250.70  
  Purchase #3 $234.49   12.553%   $263.9255   $263.93   $263.95   $263.90  
  Purchase #4 $46.59   13.492%   $52.8759   $52.88   $52.90   $52.90  
  Purchase #5 $201.86   11.206%   $224.4804   $224.48   $224.50   $224.50  
  Purchase #6 $81.33   8.162%   $87.9682   $87.97   $87.95   $88.00  
  Purchase #7 $152.75   9.436%   $167.1635   $167.16   $167.15   $167.20  
  7 purchase totals = $1,128.09       $1,235.2841   $1,235.29   $1,235.30   $1,235.40