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 $113.95   8.830%   $124.0118   $124.01   $124.00   $124.00  
  Purchase #2 $208.88   12.407%   $234.7957   $234.80   $234.80   $234.80  
  Purchase #3 $32.66   6.655%   $34.8335   $34.83   $34.85   $34.80  
  Purchase #4 $235.40   11.723%   $262.9959   $263.00   $263.00   $263.00  
  Purchase #5 $86.49   7.349%   $92.8462   $92.85   $92.85   $92.80  
  Purchase #6 $181.77   13.691%   $206.6561   $206.66   $206.65   $206.70  
  Purchase #7 $152.68   5.490%   $161.0621   $161.06   $161.05   $161.10  
  7 purchase totals = $1,011.83       $1,117.2013   $1,117.21   $1,117.20   $1,117.20