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 $195.59   12.240%   $219.5302   $219.53   $219.55   $219.50  
  Purchase #2 $93.93   8.266%   $101.6943   $101.69   $101.70   $101.70  
  Purchase #3 $163.44   11.635%   $182.4562   $182.46   $182.45   $182.50  
  Purchase #4 $189.34   3.479%   $195.9271   $195.93   $195.95   $195.90  
  Purchase #5 $134.74   10.783%   $149.269   $149.27   $149.25   $149.30  
  Purchase #6 $62.38   4.855%   $65.4085   $65.41   $65.40   $65.40  
  Purchase #7 $162.51   12.787%   $183.2902   $183.29   $183.30   $183.30  
  7 purchase totals = $1,001.93       $1,097.5755   $1,097.58   $1,097.60   $1,097.60