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 $43.68   5.356%   $46.0195   $46.02   $46.00   $46.00  
  Purchase #2 $217.72   4.285%   $227.0493   $227.05   $227.05   $227.00  
  Purchase #3 $115.68   9.318%   $126.4591   $126.46   $126.45   $126.50  
  Purchase #4 $212.79   13.238%   $240.9591   $240.96   $240.95   $241.00  
  Purchase #5 $70.25   5.147%   $73.8658   $73.87   $73.85   $73.90  
  Purchase #6 $162.77   3.645%   $168.703   $168.70   $168.70   $168.70  
  Purchase #7 $190.40   8.815%   $207.1838   $207.18   $207.20   $207.20  
  7 purchase totals = $1,013.29       $1,090.2396   $1,090.24   $1,090.20   $1,090.30