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 $200.67   3.619%   $207.9322   $207.93   $207.95   $207.90  
  Purchase #2 $236.36   3.825%   $245.4008   $245.40   $245.40   $245.40  
  Purchase #3 $59.71   13.154%   $67.5643   $67.56   $67.55   $67.60  
  Purchase #4 $65.89   9.223%   $71.967   $71.97   $71.95   $72.00  
  Purchase #5 $113.61   12.724%   $128.0657   $128.07   $128.05   $128.10  
  Purchase #6 $116.90   13.489%   $132.6686   $132.67   $132.65   $132.70  
  Purchase #7 $162.72   4.363%   $169.8195   $169.82   $169.80   $169.80  
  7 purchase totals = $955.86       $1,023.4181   $1,023.42   $1,023.35   $1,023.50