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 $119.39   3.516%   $123.5878   $123.59   $123.60   $123.60  
  Purchase #2 $182.53   10.567%   $201.8179   $201.82   $201.80   $201.80  
  Purchase #3 $61.95   9.504%   $67.8377   $67.84   $67.85   $67.80  
  Purchase #4 $68.97   10.712%   $76.3581   $76.36   $76.35   $76.40  
  Purchase #5 $166.25   6.276%   $176.6839   $176.68   $176.70   $176.70  
  Purchase #6 $113.26   5.351%   $119.3205   $119.32   $119.30   $119.30  
  Purchase #7 $28.69   11.659%   $32.035   $32.04   $32.05   $32.00  
  7 purchase totals = $741.04       $797.6409   $797.65   $797.65   $797.60