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 $184.54   9.434%   $201.9495   $201.95   $201.95   $201.90  
  Purchase #2 $87.37   10.202%   $96.2835   $96.28   $96.30   $96.30  
  Purchase #3 $179.31   7.159%   $192.1468   $192.15   $192.15   $192.10  
  Purchase #4 $185.83   7.386%   $199.5554   $199.56   $199.55   $199.60  
  Purchase #5 $225.47   9.795%   $247.5548   $247.55   $247.55   $247.60  
  Purchase #6 $23.94   5.547%   $25.268   $25.27   $25.25   $25.30  
  Purchase #7 $66.76   6.476%   $71.0834   $71.08   $71.10   $71.10  
  7 purchase totals = $953.22       $1,033.8414   $1,033.84   $1,033.85   $1,033.90