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 $216.50   7.433%   $232.5924   $232.59   $232.60   $232.60  
  Purchase #2 $151.42   12.229%   $169.9372   $169.94   $169.95   $169.90  
  Purchase #3 $195.39   3.652%   $202.5256   $202.53   $202.55   $202.50  
  Purchase #4 $90.97   4.470%   $95.0364   $95.04   $95.05   $95.00  
  Purchase #5 $175.48   10.358%   $193.6562   $193.66   $193.65   $193.70  
  Purchase #6 $113.48   8.629%   $123.2722   $123.27   $123.25   $123.30  
  Purchase #7 $223.28   10.405%   $246.5123   $246.51   $246.50   $246.50  
  7 purchase totals = $1,166.52       $1,263.5323   $1,263.54   $1,263.55   $1,263.50