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 $196.82   9.140%   $214.8093   $214.81   $214.80   $214.80  
  Purchase #2 $106.32   9.403%   $116.3173   $116.32   $116.30   $116.30  
  Purchase #3 $243.31   3.548%   $251.9426   $251.94   $251.95   $251.90  
  Purchase #4 $17.71   4.318%   $18.4747   $18.47   $18.45   $18.50  
  Purchase #5 $83.63   5.729%   $88.4212   $88.42   $88.40   $88.40  
  Purchase #6 $181.25   10.455%   $200.1997   $200.20   $200.20   $200.20  
  Purchase #7 $127.30   7.270%   $136.5547   $136.55   $136.55   $136.60  
  7 purchase totals = $956.34       $1,026.7195   $1,026.71   $1,026.65   $1,026.70