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 $196.86   8.274%   $213.1482   $213.15   $213.15   $213.10  
  Purchase #2 $245.25   7.194%   $262.8933   $262.89   $262.90   $262.90  
  Purchase #3 $33.50   8.105%   $36.2152   $36.22   $36.20   $36.20  
  Purchase #4 $152.99   5.713%   $161.7303   $161.73   $161.75   $161.70  
  Purchase #5 $48.96   6.148%   $51.9701   $51.97   $51.95   $52.00  
  Purchase #6 $104.36   8.233%   $112.952   $112.95   $112.95   $113.00  
  Purchase #7 $184.46   11.488%   $205.6508   $205.65   $205.65   $205.70  
  7 purchase totals = $966.38       $1,044.5599   $1,044.56   $1,044.55   $1,044.60