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 $44.88   11.794%   $50.1731   $50.17   $50.15   $50.20  
  Purchase #2 $230.61   7.540%   $247.998   $248.00   $248.00   $248.00  
  Purchase #3 $77.81   11.405%   $86.6842   $86.68   $86.70   $86.70  
  Purchase #4 $33.67   9.171%   $36.7579   $36.76   $36.75   $36.80  
  Purchase #5 $182.54   10.308%   $201.3562   $201.36   $201.35   $201.40  
  Purchase #6 $236.45   12.587%   $266.212   $266.21   $266.20   $266.20  
  Purchase #7 $189.98   8.831%   $206.7571   $206.76   $206.75   $206.80  
  7 purchase totals = $995.94       $1,095.9385   $1,095.94   $1,095.90   $1,096.10