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 $92.54   3.589%   $95.8613   $95.86   $95.85   $95.90  
  Purchase #2 $140.59   9.577%   $154.0543   $154.05   $154.05   $154.10  
  Purchase #3 $193.60   7.554%   $208.2245   $208.22   $208.20   $208.20  
  Purchase #4 $98.53   13.320%   $111.6542   $111.65   $111.65   $111.70  
  Purchase #5 $140.39   3.522%   $145.3345   $145.33   $145.35   $145.30  
  Purchase #6 $204.77   8.433%   $222.0383   $222.04   $222.05   $222.00  
  Purchase #7 $178.45   3.108%   $183.9962   $184.00   $184.00   $184.00  
  7 purchase totals = $1,048.87       $1,121.1633   $1,121.15   $1,121.15   $1,121.20