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 $92.69   4.637%   $96.988   $96.99   $97.00   $97.00  
  Purchase #2 $114.78   4.599%   $120.0587   $120.06   $120.05   $120.10  
  Purchase #3 $239.92   11.211%   $266.8174   $266.82   $266.80   $266.80  
  Purchase #4 $241.72   9.776%   $265.3505   $265.35   $265.35   $265.40  
  Purchase #5 $22.33   9.409%   $24.431   $24.43   $24.45   $24.40  
  Purchase #6 $173.61   9.337%   $189.82   $189.82   $189.80   $189.80  
  Purchase #7 $136.80   8.773%   $148.8015   $148.80   $148.80   $148.80  
  7 purchase totals = $1,021.85       $1,112.2671   $1,112.27   $1,112.25   $1,112.30