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 $214.38   8.776%   $233.194   $233.19   $233.20   $233.20  
  Purchase #2 $249.35   11.613%   $278.307   $278.31   $278.30   $278.30  
  Purchase #3 $82.87   3.431%   $85.7133   $85.71   $85.70   $85.70  
  Purchase #4 $144.43   13.415%   $163.8053   $163.81   $163.80   $163.80  
  Purchase #5 $92.81   13.479%   $105.3199   $105.32   $105.30   $105.30  
  Purchase #6 $55.45   13.370%   $62.8637   $62.86   $62.85   $62.90  
  Purchase #7 $185.81   9.248%   $202.9937   $202.99   $203.00   $203.00  
  7 purchase totals = $1,025.10       $1,132.1969   $1,132.19   $1,132.15   $1,132.20