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 $53.70   9.218%   $58.6501   $58.65   $58.65   $58.70  
  Purchase #2 $180.61   12.239%   $202.7149   $202.71   $202.70   $202.70  
  Purchase #3 $209.55   6.617%   $223.4159   $223.42   $223.40   $223.40  
  Purchase #4 $171.48   8.133%   $185.4265   $185.43   $185.45   $185.40  
  Purchase #5 $67.63   7.619%   $72.7827   $72.78   $72.80   $72.80  
  Purchase #6 $173.86   5.292%   $183.0607   $183.06   $183.05   $183.10  
  Purchase #7 $212.82   4.727%   $222.88   $222.88   $222.90   $222.90  
  7 purchase totals = $1,069.65       $1,148.9308   $1,148.93   $1,148.95   $1,149.00