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 $184.87   5.786%   $195.5666   $195.57   $195.55   $195.60  
  Purchase #2 $114.77   4.487%   $119.9197   $119.92   $119.90   $119.90  
  Purchase #3 $63.25   9.517%   $69.2695   $69.27   $69.25   $69.30  
  Purchase #4 $78.61   4.249%   $81.9501   $81.95   $81.95   $82.00  
  Purchase #5 $136.82   3.399%   $141.4705   $141.47   $141.45   $141.50  
  Purchase #6 $220.91   6.425%   $235.1035   $235.10   $235.10   $235.10  
  Purchase #7 $212.43   6.816%   $226.9092   $226.91   $226.90   $226.90  
  7 purchase totals = $1,011.66       $1,070.1891   $1,070.19   $1,070.10   $1,070.30