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 $203.25   5.313%   $214.0487   $214.05   $214.05   $214.00  
  Purchase #2 $179.54   8.367%   $194.5621   $194.56   $194.55   $194.60  
  Purchase #3 $28.47   5.508%   $30.0381   $30.04   $30.05   $30.00  
  Purchase #4 $81.96   6.739%   $87.4833   $87.48   $87.50   $87.50  
  Purchase #5 $228.40   13.717%   $259.7296   $259.73   $259.75   $259.70  
  Purchase #6 $197.80   11.643%   $220.8299   $220.83   $220.85   $220.80  
  Purchase #7 $90.81   4.824%   $95.1907   $95.19   $95.20   $95.20  
  7 purchase totals = $1,010.23       $1,101.8824   $1,101.88   $1,101.95   $1,101.80