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 $196.27   7.684%   $211.3514   $211.35   $211.35   $211.40  
  Purchase #2 $80.57   8.381%   $87.3226   $87.32   $87.30   $87.30  
  Purchase #3 $156.58   12.359%   $175.9317   $175.93   $175.95   $175.90  
  Purchase #4 $151.96   3.451%   $157.2041   $157.20   $157.20   $157.20  
  Purchase #5 $95.36   5.335%   $100.4475   $100.45   $100.45   $100.40  
  Purchase #6 $233.62   13.423%   $264.9788   $264.98   $265.00   $265.00  
  Purchase #7 $42.50   11.139%   $47.2341   $47.23   $47.25   $47.20  
  7 purchase totals = $956.86       $1,044.4702   $1,044.46   $1,044.50   $1,044.40