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 $60.68   3.167%   $62.6017   $62.60   $62.60   $62.60  
  Purchase #2 $248.63   10.872%   $275.6611   $275.66   $275.65   $275.70  
  Purchase #3 $230.61   5.222%   $242.6525   $242.65   $242.65   $242.70  
  Purchase #4 $184.26   13.864%   $209.8058   $209.81   $209.80   $209.80  
  Purchase #5 $85.47   3.244%   $88.2426   $88.24   $88.25   $88.20  
  Purchase #6 $171.66   12.289%   $192.7553   $192.76   $192.75   $192.80  
  Purchase #7 $56.51   12.108%   $63.3522   $63.35   $63.35   $63.40  
  7 purchase totals = $1,037.82       $1,135.0712   $1,135.07   $1,135.05   $1,135.20