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 $196.31   8.788%   $213.5617   $213.56   $213.55   $213.60  
  Purchase #2 $231.34   4.345%   $241.3917   $241.39   $241.40   $241.40  
  Purchase #3 $210.94   8.722%   $229.3382   $229.34   $229.35   $229.30  
  Purchase #4 $58.53   3.507%   $60.5826   $60.58   $60.60   $60.60  
  Purchase #5 $191.50   6.260%   $203.4879   $203.49   $203.50   $203.50  
  Purchase #6 $70.83   6.696%   $75.5728   $75.57   $75.55   $75.60  
  Purchase #7 $93.25   6.240%   $99.0688   $99.07   $99.05   $99.10  
  7 purchase totals = $1,052.70       $1,123.0037   $1,123.00   $1,123.00   $1,123.10