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 $88.71   4.384%   $92.599   $92.60   $92.60   $92.60  
  Purchase #2 $211.99   5.130%   $222.8651   $222.87   $222.85   $222.90  
  Purchase #3 $69.89   5.670%   $73.8528   $73.85   $73.85   $73.90  
  Purchase #4 $6.51   3.257%   $6.722   $6.72   $6.70   $6.70  
  Purchase #5 $102.63   4.117%   $106.8553   $106.86   $106.85   $106.90  
  Purchase #6 $199.76   5.677%   $211.1004   $211.10   $211.10   $211.10  
  Purchase #7 $81.77   12.603%   $92.0755   $92.08   $92.10   $92.10  
  7 purchase totals = $761.26       $806.0701   $806.08   $806.05   $806.20