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 $103.69   10.551%   $114.6303   $114.63   $114.65   $114.60  
  Purchase #2 $147.76   8.760%   $160.7038   $160.70   $160.70   $160.70  
  Purchase #3 $168.51   11.539%   $187.9544   $187.95   $187.95   $188.00  
  Purchase #4 $37.42   3.271%   $38.644   $38.64   $38.65   $38.60  
  Purchase #5 $86.51   5.794%   $91.5224   $91.52   $91.50   $91.50  
  Purchase #6 $173.43   8.180%   $187.6166   $187.62   $187.60   $187.60  
  Purchase #7 $168.91   6.342%   $179.6223   $179.62   $179.60   $179.60  
  7 purchase totals = $886.23       $960.6938   $960.68   $960.65   $960.60