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 $183.40   7.452%   $197.067   $197.07   $197.05   $197.10  
  Purchase #2 $120.62   13.298%   $136.66   $136.66   $136.65   $136.70  
  Purchase #3 $102.34   13.867%   $116.5315   $116.53   $116.55   $116.50  
  Purchase #4 $81.75   13.705%   $92.9538   $92.95   $92.95   $93.00  
  Purchase #5 $212.87   4.701%   $222.877   $222.88   $222.90   $222.90  
  Purchase #6 $111.59   3.501%   $115.4968   $115.50   $115.50   $115.50  
  Purchase #7 $43.48   13.230%   $49.2324   $49.23   $49.25   $49.20  
  7 purchase totals = $856.05       $930.8185   $930.82   $930.85   $930.90