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 $232.26   13.523%   $263.6685   $263.67   $263.65   $263.70  
  Purchase #2 $42.69   7.109%   $45.7248   $45.72   $45.70   $45.70  
  Purchase #3 $112.32   11.832%   $125.6097   $125.61   $125.60   $125.60  
  Purchase #4 $174.26   10.302%   $192.2123   $192.21   $192.20   $192.20  
  Purchase #5 $92.87   6.466%   $98.875   $98.88   $98.90   $98.90  
  Purchase #6 $118.70   5.765%   $125.5431   $125.54   $125.55   $125.50  
  Purchase #7 $40.70   6.832%   $43.4806   $43.48   $43.50   $43.50  
  7 purchase totals = $813.80       $895.1140   $895.11   $895.10   $895.10