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 $82.47   3.470%   $85.3317   $85.33   $85.35   $85.30  
  Purchase #2 $213.30   10.421%   $235.528   $235.53   $235.55   $235.50  
  Purchase #3 $76.51   6.807%   $81.718   $81.72   $81.70   $81.70  
  Purchase #4 $208.86   5.491%   $220.3285   $220.33   $220.35   $220.30  
  Purchase #5 $211.60   13.106%   $239.3323   $239.33   $239.35   $239.30  
  Purchase #6 $145.87   13.438%   $165.472   $165.47   $165.45   $165.50  
  Purchase #7 $30.40   5.362%   $32.03   $32.03   $32.05   $32.00  
  7 purchase totals = $969.01       $1,059.7405   $1,059.74   $1,059.80   $1,059.60