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 $184.28   9.355%   $201.5194   $201.52   $201.50   $201.50  
  Purchase #2 $218.58   13.383%   $247.8326   $247.83   $247.85   $247.80  
  Purchase #3 $173.68   11.354%   $193.3996   $193.40   $193.40   $193.40  
  Purchase #4 $45.53   7.823%   $49.0918   $49.09   $49.10   $49.10  
  Purchase #5 $56.80   6.738%   $60.6272   $60.63   $60.65   $60.60  
  Purchase #6 $230.99   5.406%   $243.4773   $243.48   $243.50   $243.50  
  Purchase #7 $183.64   9.293%   $200.7057   $200.71   $200.70   $200.70  
  7 purchase totals = $1,093.50       $1,196.6536   $1,196.66   $1,196.70   $1,196.60