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 $72.98   5.205%   $76.7786   $76.78   $76.80   $76.80  
  Purchase #2 $208.43   13.827%   $237.2496   $237.25   $237.25   $237.20  
  Purchase #3 $112.65   10.229%   $124.173   $124.17   $124.15   $124.20  
  Purchase #4 $126.82   9.522%   $138.8958   $138.90   $138.90   $138.90  
  Purchase #5 $212.75   10.821%   $235.7717   $235.77   $235.75   $235.80  
  Purchase #6 $149.74   12.505%   $168.465   $168.47   $168.45   $168.50  
  Purchase #7 $21.55   11.334%   $23.9925   $23.99   $24.00   $24.00  
  7 purchase totals = $904.92       $1,005.3262   $1,005.33   $1,005.30   $1,005.40