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 $195.41   3.273%   $201.8058   $201.81   $201.80   $201.80  
  Purchase #2 $92.27   6.196%   $97.987   $97.99   $98.00   $98.00  
  Purchase #3 $211.85   3.350%   $218.947   $218.95   $218.95   $218.90  
  Purchase #4 $21.46   8.424%   $23.2678   $23.27   $23.25   $23.30  
  Purchase #5 $60.95   3.536%   $63.1052   $63.11   $63.10   $63.10  
  Purchase #6 $20.45   7.657%   $22.0159   $22.02   $22.00   $22.00  
  Purchase #7 $25.88   7.787%   $27.8953   $27.90   $27.90   $27.90  
  7 purchase totals = $628.27       $655.0240   $655.05   $655.00   $655.00