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 $188.57   6.613%   $201.0401   $201.04   $201.05   $201.00  
  Purchase #2 $229.74   9.712%   $252.0523   $252.05   $252.05   $252.10  
  Purchase #3 $157.36   9.274%   $171.9536   $171.95   $171.95   $172.00  
  Purchase #4 $189.70   5.122%   $199.4164   $199.42   $199.40   $199.40  
  Purchase #5 $131.30   11.805%   $146.8   $146.80   $146.80   $146.80  
  Purchase #6 $173.44   3.476%   $179.4688   $179.47   $179.45   $179.50  
  Purchase #7 $61.34   3.153%   $63.2741   $63.27   $63.25   $63.30  
  7 purchase totals = $1,131.45       $1,214.0053   $1,214.00   $1,213.95   $1,214.10