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 $196.57   6.144%   $208.6473   $208.65   $208.65   $208.60  
  Purchase #2 $217.61   10.188%   $239.7801   $239.78   $239.80   $239.80  
  Purchase #3 $36.61   13.639%   $41.6032   $41.60   $41.60   $41.60  
  Purchase #4 $176.86   4.319%   $184.4986   $184.50   $184.50   $184.50  
  Purchase #5 $149.52   12.325%   $167.9483   $167.95   $167.95   $167.90  
  Purchase #6 $219.67   8.588%   $238.5353   $238.54   $238.55   $238.50  
  Purchase #7 $106.69   6.500%   $113.6249   $113.62   $113.60   $113.60  
  7 purchase totals = $1,103.53       $1,194.6377   $1,194.64   $1,194.65   $1,194.50