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 $71.30   9.275%   $77.9131   $77.91   $77.90   $77.90  
  Purchase #2 $203.32   11.622%   $226.9499   $226.95   $226.95   $226.90  
  Purchase #3 $154.48   5.203%   $162.5176   $162.52   $162.50   $162.50  
  Purchase #4 $41.86   4.618%   $43.7931   $43.79   $43.80   $43.80  
  Purchase #5 $234.55   3.284%   $242.2526   $242.25   $242.25   $242.30  
  Purchase #6 $245.64   6.410%   $261.3855   $261.39   $261.40   $261.40  
  Purchase #7 $163.83   10.398%   $180.865   $180.87   $180.85   $180.90  
  7 purchase totals = $1,114.98       $1,195.6768   $1,195.68   $1,195.65   $1,195.70