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 $226.27   8.630%   $245.7971   $245.80   $245.80   $245.80  
  Purchase #2 $210.39   10.585%   $232.6598   $232.66   $232.65   $232.70  
  Purchase #3 $172.89   8.558%   $187.6859   $187.69   $187.70   $187.70  
  Purchase #4 $73.27   10.458%   $80.9326   $80.93   $80.95   $80.90  
  Purchase #5 $208.50   5.346%   $219.6464   $219.65   $219.65   $219.60  
  Purchase #6 $30.63   8.265%   $33.1616   $33.16   $33.15   $33.20  
  Purchase #7 $56.28   7.771%   $60.6535   $60.65   $60.65   $60.70  
  7 purchase totals = $978.23       $1,060.5369   $1,060.54   $1,060.55   $1,060.60