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 $82.80   13.822%   $94.2446   $94.24   $94.25   $94.20  
  Purchase #2 $206.32   8.280%   $223.4033   $223.40   $223.40   $223.40  
  Purchase #3 $234.37   4.549%   $245.0315   $245.03   $245.05   $245.00  
  Purchase #4 $151.97   6.168%   $161.3435   $161.34   $161.35   $161.30  
  Purchase #5 $78.91   10.212%   $86.9683   $86.97   $86.95   $87.00  
  Purchase #6 $238.65   10.734%   $264.2667   $264.27   $264.25   $264.30  
  Purchase #7 $132.48   5.425%   $139.667   $139.67   $139.65   $139.70  
  7 purchase totals = $1,125.50       $1,214.9249   $1,214.92   $1,214.90   $1,214.90