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 $88.99   7.414%   $95.5877   $95.59   $95.60   $95.60  
  Purchase #2 $155.37   5.281%   $163.5751   $163.58   $163.60   $163.60  
  Purchase #3 $157.58   9.811%   $173.0402   $173.04   $173.05   $173.00  
  Purchase #4 $23.77   10.479%   $26.2609   $26.26   $26.25   $26.30  
  Purchase #5 $246.45   5.135%   $259.1052   $259.11   $259.10   $259.10  
  Purchase #6 $185.72   12.777%   $209.4494   $209.45   $209.45   $209.40  
  Purchase #7 $178.43   5.345%   $187.9671   $187.97   $187.95   $188.00  
  7 purchase totals = $1,036.31       $1,114.9856   $1,115.00   $1,115.00   $1,115.00