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 $58.34   5.746%   $61.6922   $61.69   $61.70   $61.70  
  Purchase #2 $168.94   8.167%   $182.7373   $182.74   $182.75   $182.70  
  Purchase #3 $116.32   12.291%   $130.6169   $130.62   $130.60   $130.60  
  Purchase #4 $93.62   13.701%   $106.4469   $106.45   $106.45   $106.40  
  Purchase #5 $129.66   12.642%   $146.0516   $146.05   $146.05   $146.10  
  Purchase #6 $201.95   10.235%   $222.6196   $222.62   $222.60   $222.60  
  Purchase #7 $189.64   12.728%   $213.7774   $213.78   $213.80   $213.80  
  7 purchase totals = $958.47       $1,063.9419   $1,063.95   $1,063.95   $1,063.90