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 $68.28   11.243%   $75.9567   $75.96   $75.95   $76.00  
  Purchase #2 $239.99   9.332%   $262.3859   $262.39   $262.40   $262.40  
  Purchase #3 $201.83   10.797%   $223.6216   $223.62   $223.60   $223.60  
  Purchase #4 $149.80   7.126%   $160.4747   $160.47   $160.45   $160.50  
  Purchase #5 $113.60   8.785%   $123.5798   $123.58   $123.60   $123.60  
  Purchase #6 $68.59   10.111%   $75.5251   $75.53   $75.55   $75.50  
  Purchase #7 $161.93   11.295%   $180.22   $180.22   $180.20   $180.20  
  7 purchase totals = $1,004.02       $1,101.7638   $1,101.77   $1,101.75   $1,101.80