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 $96.39   8.525%   $104.6072   $104.61   $104.60   $104.60  
  Purchase #2 $200.94   8.346%   $217.7105   $217.71   $217.70   $217.70  
  Purchase #3 $49.28   9.230%   $53.8285   $53.83   $53.85   $53.80  
  Purchase #4 $183.52   4.448%   $191.683   $191.68   $191.70   $191.70  
  Purchase #5 $248.34   6.305%   $263.9978   $264.00   $264.00   $264.00  
  Purchase #6 $97.47   13.536%   $110.6635   $110.66   $110.65   $110.70  
  Purchase #7 $215.85   5.269%   $227.2231   $227.22   $227.20   $227.20  
  7 purchase totals = $1,091.79       $1,169.7136   $1,169.71   $1,169.70   $1,169.70