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 $33.97   5.707%   $35.9087   $35.91   $35.90   $35.90  
  Purchase #2 $218.33   13.108%   $246.9487   $246.95   $246.95   $246.90  
  Purchase #3 $240.50   10.299%   $265.2691   $265.27   $265.25   $265.30  
  Purchase #4 $72.74   11.628%   $81.1982   $81.20   $81.20   $81.20  
  Purchase #5 $97.53   9.137%   $106.4413   $106.44   $106.45   $106.40  
  Purchase #6 $113.40   3.627%   $117.513   $117.51   $117.50   $117.50  
  Purchase #7 $141.87   13.716%   $161.3289   $161.33   $161.35   $161.30  
  7 purchase totals = $918.34       $1,014.6079   $1,014.61   $1,014.60   $1,014.50