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 $193.84   10.600%   $214.387   $214.39   $214.40   $214.40  
  Purchase #2 $111.71   9.433%   $122.2476   $122.25   $122.25   $122.20  
  Purchase #3 $69.62   7.155%   $74.6013   $74.60   $74.60   $74.60  
  Purchase #4 $201.99   6.227%   $214.5679   $214.57   $214.55   $214.60  
  Purchase #5 $90.68   11.308%   $100.9341   $100.93   $100.95   $100.90  
  Purchase #6 $44.62   4.506%   $46.6306   $46.63   $46.65   $46.60  
  Purchase #7 $154.53   8.516%   $167.6898   $167.69   $167.70   $167.70  
  7 purchase totals = $866.99       $941.0583   $941.06   $941.10   $941.00