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 $185.93   5.401%   $195.9721   $195.97   $195.95   $196.00  
  Purchase #2 $112.85   10.733%   $124.9622   $124.96   $124.95   $125.00  
  Purchase #3 $28.40   6.512%   $30.2494   $30.25   $30.25   $30.20  
  Purchase #4 $239.90   11.580%   $267.6804   $267.68   $267.70   $267.70  
  Purchase #5 $167.64   11.458%   $186.8482   $186.85   $186.85   $186.80  
  Purchase #6 $97.73   6.595%   $104.1753   $104.18   $104.20   $104.20  
  Purchase #7 $107.32   8.819%   $116.7846   $116.78   $116.80   $116.80  
  7 purchase totals = $939.77       $1,026.6722   $1,026.67   $1,026.70   $1,026.70