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 $247.77   6.586%   $264.0881   $264.09   $264.10   $264.10  
  Purchase #2 $41.91   7.473%   $45.0419   $45.04   $45.05   $45.00  
  Purchase #3 $200.30   7.150%   $214.6215   $214.62   $214.60   $214.60  
  Purchase #4 $111.71   6.512%   $118.9846   $118.98   $119.00   $119.00  
  Purchase #5 $217.81   5.202%   $229.1405   $229.14   $229.15   $229.10  
  Purchase #6 $165.72   13.296%   $187.7541   $187.75   $187.75   $187.80  
  Purchase #7 $88.44   6.438%   $94.1338   $94.13   $94.15   $94.10  
  7 purchase totals = $1,073.66       $1,153.7645   $1,153.75   $1,153.80   $1,153.70