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 $59.34   3.162%   $61.2163   $61.22   $61.20   $61.20  
  Purchase #2 $242.42   8.251%   $262.4221   $262.42   $262.40   $262.40  
  Purchase #3 $95.74   6.685%   $102.1402   $102.14   $102.15   $102.10  
  Purchase #4 $240.26   9.747%   $263.6781   $263.68   $263.70   $263.70  
  Purchase #5 $56.89   13.190%   $64.3938   $64.39   $64.40   $64.40  
  Purchase #6 $181.26   9.133%   $197.8145   $197.81   $197.80   $197.80  
  Purchase #7 $49.37   12.158%   $55.3724   $55.37   $55.35   $55.40  
  7 purchase totals = $925.28       $1,007.0374   $1,007.03   $1,007.00   $1,007.00