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 $59.61   3.453%   $61.6683   $61.67   $61.65   $61.70  
  Purchase #2 $188.78   13.826%   $214.8807   $214.88   $214.90   $214.90  
  Purchase #3 $98.52   6.272%   $104.6992   $104.70   $104.70   $104.70  
  Purchase #4 $12.65   8.516%   $13.7273   $13.73   $13.75   $13.70  
  Purchase #5 $134.85   13.170%   $152.6097   $152.61   $152.60   $152.60  
  Purchase #6 $174.96   6.435%   $186.2187   $186.22   $186.20   $186.20  
  Purchase #7 $30.79   4.425%   $32.1525   $32.15   $32.15   $32.20  
  7 purchase totals = $700.16       $765.9564   $765.96   $765.95   $766.00