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 $59.79   5.466%   $63.0581   $63.06   $63.05   $63.10  
  Purchase #2 $183.53   7.251%   $196.8378   $196.84   $196.85   $196.80  
  Purchase #3 $58.55   7.362%   $62.8605   $62.86   $62.85   $62.90  
  Purchase #4 $218.30   11.352%   $243.0814   $243.08   $243.10   $243.10  
  Purchase #5 $183.89   4.103%   $191.435   $191.44   $191.45   $191.40  
  Purchase #6 $101.63   3.290%   $104.9736   $104.97   $104.95   $105.00  
  Purchase #7 $93.54   8.723%   $101.6995   $101.70   $101.70   $101.70  
  7 purchase totals = $899.23       $963.9459   $963.95   $963.95   $964.00