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 $230.71   11.670%   $257.6339   $257.63   $257.65   $257.60  
  Purchase #2 $168.96   8.178%   $182.7775   $182.78   $182.80   $182.80  
  Purchase #3 $43.33   13.459%   $49.1618   $49.16   $49.15   $49.20  
  Purchase #4 $245.57   10.177%   $270.5617   $270.56   $270.55   $270.60  
  Purchase #5 $157.52   5.535%   $166.2387   $166.24   $166.25   $166.20  
  Purchase #6 $5.86   5.457%   $6.1798   $6.18   $6.20   $6.20  
  Purchase #7 $77.85   5.520%   $82.1473   $82.15   $82.15   $82.10  
  7 purchase totals = $929.80       $1,014.7007   $1,014.70   $1,014.75   $1,014.70