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 $58.86   3.624%   $60.9931   $60.99   $61.00   $61.00  
  Purchase #2 $233.89   10.331%   $258.0532   $258.05   $258.05   $258.10  
  Purchase #3 $205.81   3.779%   $213.5876   $213.59   $213.60   $213.60  
  Purchase #4 $116.63   8.287%   $126.2951   $126.30   $126.30   $126.30  
  Purchase #5 $147.55   6.345%   $156.912   $156.91   $156.90   $156.90  
  Purchase #6 $187.57   10.532%   $207.3249   $207.32   $207.30   $207.30  
  Purchase #7 $9.39   3.336%   $9.7033   $9.70   $9.70   $9.70  
  7 purchase totals = $959.70       $1,032.8692   $1,032.86   $1,032.85   $1,032.90