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 $217.92   6.479%   $232.039   $232.04   $232.05   $232.00  
  Purchase #2 $43.97   8.261%   $47.6024   $47.60   $47.60   $47.60  
  Purchase #3 $107.25   8.259%   $116.1078   $116.11   $116.10   $116.10  
  Purchase #4 $125.78   13.305%   $142.515   $142.52   $142.50   $142.50  
  Purchase #5 $182.87   8.777%   $198.9205   $198.92   $198.90   $198.90  
  Purchase #6 $241.56   5.848%   $255.6864   $255.69   $255.70   $255.70  
  Purchase #7 $248.41   7.810%   $267.8108   $267.81   $267.80   $267.80  
  7 purchase totals = $1,167.76       $1,260.6819   $1,260.69   $1,260.65   $1,260.60