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 $208.48   9.275%   $227.8165   $227.82   $227.80   $227.80  
  Purchase #2 $35.66   8.210%   $38.5877   $38.59   $38.60   $38.60  
  Purchase #3 $213.38   5.351%   $224.798   $224.80   $224.80   $224.80  
  Purchase #4 $248.40   8.382%   $269.2209   $269.22   $269.20   $269.20  
  Purchase #5 $18.65   3.654%   $19.3315   $19.33   $19.35   $19.30  
  Purchase #6 $161.86   11.835%   $181.0161   $181.02   $181.00   $181.00  
  Purchase #7 $187.42   8.404%   $203.1708   $203.17   $203.15   $203.20  
  7 purchase totals = $1,073.85       $1,163.9415   $1,163.95   $1,163.90   $1,163.90