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 $85.71   11.738%   $95.7706   $95.77   $95.75   $95.80  
  Purchase #2 $162.52   11.524%   $181.2488   $181.25   $181.25   $181.20  
  Purchase #3 $193.99   10.137%   $213.6548   $213.65   $213.65   $213.70  
  Purchase #4 $74.98   3.853%   $77.869   $77.87   $77.85   $77.90  
  Purchase #5 $214.80   9.183%   $234.5251   $234.53   $234.55   $234.50  
  Purchase #6 $236.47   7.281%   $253.6874   $253.69   $253.70   $253.70  
  Purchase #7 $88.80   4.309%   $92.6264   $92.63   $92.65   $92.60  
  7 purchase totals = $1,057.27       $1,149.3821   $1,149.39   $1,149.40   $1,149.40