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 $179.37   9.131%   $195.7483   $195.75   $195.75   $195.70  
  Purchase #2 $141.76   3.415%   $146.6011   $146.60   $146.60   $146.60  
  Purchase #3 $204.42   9.871%   $224.5983   $224.60   $224.60   $224.60  
  Purchase #4 $54.27   4.764%   $56.8554   $56.86   $56.85   $56.90  
  Purchase #5 $168.75   9.802%   $185.2909   $185.29   $185.30   $185.30  
  Purchase #6 $124.95   8.799%   $135.9444   $135.94   $135.95   $135.90  
  Purchase #7 $225.88   3.248%   $233.2166   $233.22   $233.20   $233.20  
  7 purchase totals = $1,099.40       $1,178.2550   $1,178.26   $1,178.25   $1,178.20