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 $215.81   9.366%   $236.0228   $236.02   $236.00   $236.00  
  Purchase #2 $124.81   12.419%   $140.3102   $140.31   $140.30   $140.30  
  Purchase #3 $43.77   6.703%   $46.7039   $46.70   $46.70   $46.70  
  Purchase #4 $110.77   5.352%   $116.6984   $116.70   $116.70   $116.70  
  Purchase #5 $78.73   7.202%   $84.4001   $84.40   $84.40   $84.40  
  Purchase #6 $152.64   13.655%   $173.483   $173.48   $173.50   $173.50  
  Purchase #7 $203.82   4.730%   $213.4607   $213.46   $213.45   $213.50  
  7 purchase totals = $930.35       $1,011.0791   $1,011.07   $1,011.05   $1,011.10