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 $44.52   3.249%   $45.9665   $45.97   $45.95   $46.00  
  Purchase #2 $109.62   12.224%   $123.0199   $123.02   $123.00   $123.00  
  Purchase #3 $242.47   3.661%   $251.3468   $251.35   $251.35   $251.30  
  Purchase #4 $217.95   7.391%   $234.0587   $234.06   $234.05   $234.10  
  Purchase #5 $114.95   8.364%   $124.5644   $124.56   $124.55   $124.60  
  Purchase #6 $235.82   6.552%   $251.2709   $251.27   $251.25   $251.30  
  Purchase #7 $61.44   3.719%   $63.725   $63.73   $63.75   $63.70  
  7 purchase totals = $1,026.77       $1,093.9522   $1,093.96   $1,093.90   $1,094.00