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 $59.27   7.301%   $63.5973   $63.60   $63.60   $63.60  
  Purchase #2 $189.81   4.708%   $198.7463   $198.75   $198.75   $198.70  
  Purchase #3 $126.47   8.363%   $137.0467   $137.05   $137.05   $137.00  
  Purchase #4 $173.51   3.645%   $179.8344   $179.83   $179.85   $179.80  
  Purchase #5 $75.30   8.119%   $81.4136   $81.41   $81.40   $81.40  
  Purchase #6 $159.42   12.235%   $178.925   $178.93   $178.95   $178.90  
  Purchase #7 $241.31   5.540%   $254.6786   $254.68   $254.70   $254.70  
  7 purchase totals = $1,025.09       $1,094.2419   $1,094.25   $1,094.30   $1,094.10