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 $62.64   11.290%   $69.7121   $69.71   $69.70   $69.70  
  Purchase #2 $242.77   13.690%   $276.0052   $276.01   $276.00   $276.00  
  Purchase #3 $88.59   3.295%   $91.509   $91.51   $91.50   $91.50  
  Purchase #4 $224.69   12.562%   $252.9156   $252.92   $252.90   $252.90  
  Purchase #5 $23.48   10.485%   $25.9419   $25.94   $25.95   $25.90  
  Purchase #6 $53.57   12.104%   $60.0541   $60.05   $60.05   $60.10  
  Purchase #7 $166.79   12.137%   $187.0333   $187.03   $187.05   $187.00  
  7 purchase totals = $862.53       $963.1712   $963.17   $963.15   $963.10