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 $87.67   10.421%   $96.8061   $96.81   $96.80   $96.80  
  Purchase #2 $176.43   9.760%   $193.6496   $193.65   $193.65   $193.60  
  Purchase #3 $222.57   11.755%   $248.7331   $248.73   $248.75   $248.70  
  Purchase #4 $185.71   6.221%   $197.263   $197.26   $197.25   $197.30  
  Purchase #5 $247.57   7.354%   $265.7763   $265.78   $265.80   $265.80  
  Purchase #6 $104.91   10.402%   $115.8227   $115.82   $115.80   $115.80  
  Purchase #7 $203.94   13.527%   $231.527   $231.53   $231.55   $231.50  
  7 purchase totals = $1,228.80       $1,349.5778   $1,349.58   $1,349.60   $1,349.50