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 $197.61   8.190%   $213.7943   $213.79   $213.80   $213.80  
  Purchase #2 $213.62   10.596%   $236.2552   $236.26   $236.25   $236.30  
  Purchase #3 $62.81   4.518%   $65.6478   $65.65   $65.65   $65.60  
  Purchase #4 $121.37   3.468%   $125.5791   $125.58   $125.60   $125.60  
  Purchase #5 $200.49   7.796%   $216.1202   $216.12   $216.10   $216.10  
  Purchase #6 $49.50   6.492%   $52.7135   $52.71   $52.70   $52.70  
  Purchase #7 $237.72   11.491%   $265.0364   $265.04   $265.05   $265.00  
  7 purchase totals = $1,083.12       $1,175.1465   $1,175.15   $1,175.15   $1,175.10