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 $67.84   10.102%   $74.6932   $74.69   $74.70   $74.70  
  Purchase #2 $88.64   6.569%   $94.4628   $94.46   $94.45   $94.50  
  Purchase #3 $162.63   12.505%   $182.9669   $182.97   $182.95   $183.00  
  Purchase #4 $60.77   7.668%   $65.4298   $65.43   $65.45   $65.40  
  Purchase #5 $225.27   10.601%   $249.1509   $249.15   $249.15   $249.20  
  Purchase #6 $164.54   5.613%   $173.7756   $173.78   $173.80   $173.80  
  Purchase #7 $162.78   11.733%   $181.879   $181.88   $181.90   $181.90  
  7 purchase totals = $932.47       $1,022.3582   $1,022.36   $1,022.40   $1,022.50