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 $117.80   6.554%   $125.5206   $125.52   $125.50   $125.50  
  Purchase #2 $151.25   5.183%   $159.0893   $159.09   $159.10   $159.10  
  Purchase #3 $151.58   7.565%   $163.047   $163.05   $163.05   $163.00  
  Purchase #4 $214.59   3.192%   $221.4397   $221.44   $221.45   $221.40  
  Purchase #5 $118.41   4.847%   $124.1493   $124.15   $124.15   $124.10  
  Purchase #6 $190.30   13.569%   $216.1218   $216.12   $216.10   $216.10  
  Purchase #7 $24.77   6.625%   $26.411   $26.41   $26.40   $26.40  
  7 purchase totals = $968.70       $1,035.7787   $1,035.78   $1,035.75   $1,035.60