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 $179.34   8.719%   $194.9767   $194.98   $195.00   $195.00  
  Purchase #2 $210.31   9.379%   $230.035   $230.04   $230.05   $230.00  
  Purchase #3 $49.90   12.625%   $56.1999   $56.20   $56.20   $56.20  
  Purchase #4 $57.65   3.394%   $59.6066   $59.61   $59.60   $59.60  
  Purchase #5 $46.82   8.295%   $50.7037   $50.70   $50.70   $50.70  
  Purchase #6 $192.42   11.417%   $214.3886   $214.39   $214.40   $214.40  
  Purchase #7 $217.55   9.608%   $238.4522   $238.45   $238.45   $238.50  
  7 purchase totals = $953.99       $1,044.3627   $1,044.37   $1,044.40   $1,044.40