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 $60.98   4.135%   $63.5015   $63.50   $63.50   $63.50  
  Purchase #2 $228.29   10.656%   $252.6166   $252.62   $252.60   $252.60  
  Purchase #3 $231.75   13.309%   $262.5936   $262.59   $262.60   $262.60  
  Purchase #4 $54.55   4.691%   $57.1089   $57.11   $57.10   $57.10  
  Purchase #5 $169.67   10.252%   $187.0646   $187.06   $187.05   $187.10  
  Purchase #6 $147.46   8.225%   $159.5886   $159.59   $159.60   $159.60  
  Purchase #7 $112.79   3.243%   $116.4478   $116.45   $116.45   $116.40  
  7 purchase totals = $1,005.49       $1,098.9216   $1,098.92   $1,098.90   $1,098.90