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 $41.28   9.312%   $45.124   $45.12   $45.10   $45.10  
  Purchase #2 $156.56   3.193%   $161.559   $161.56   $161.55   $161.60  
  Purchase #3 $223.37   6.395%   $237.6545   $237.65   $237.65   $237.70  
  Purchase #4 $243.73   6.628%   $259.8844   $259.88   $259.90   $259.90  
  Purchase #5 $138.90   13.446%   $157.5765   $157.58   $157.60   $157.60  
  Purchase #6 $160.81   6.562%   $171.3624   $171.36   $171.35   $171.40  
  Purchase #7 $214.94   7.201%   $230.4178   $230.42   $230.40   $230.40  
  7 purchase totals = $1,179.59       $1,263.5786   $1,263.57   $1,263.55   $1,263.70