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 $232.29   5.622%   $245.3493   $245.35   $245.35   $245.30  
  Purchase #2 $23.82   9.159%   $26.0017   $26.00   $26.00   $26.00  
  Purchase #3 $131.45   6.494%   $139.9864   $139.99   $140.00   $140.00  
  Purchase #4 $70.79   8.174%   $76.5764   $76.58   $76.60   $76.60  
  Purchase #5 $205.80   3.450%   $212.9001   $212.90   $212.90   $212.90  
  Purchase #6 $116.57   4.416%   $121.7177   $121.72   $121.70   $121.70  
  Purchase #7 $186.86   7.397%   $200.682   $200.68   $200.70   $200.70  
  7 purchase totals = $967.58       $1,023.2136   $1,023.22   $1,023.25   $1,023.20