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 $174.46   11.183%   $193.9699   $193.97   $193.95   $194.00  
  Purchase #2 $130.86   10.759%   $144.9392   $144.94   $144.95   $144.90  
  Purchase #3 $151.37   6.733%   $161.5617   $161.56   $161.55   $161.60  
  Purchase #4 $54.50   4.359%   $56.8757   $56.88   $56.90   $56.90  
  Purchase #5 $141.58   8.674%   $153.8606   $153.86   $153.85   $153.90  
  Purchase #6 $142.97   13.294%   $161.9764   $161.98   $162.00   $162.00  
  Purchase #7 $39.25   11.401%   $43.7249   $43.72   $43.70   $43.70  
  7 purchase totals = $834.99       $916.9084   $916.91   $916.90   $917.00