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 $65.28   10.239%   $71.964   $71.96   $71.95   $72.00  
  Purchase #2 $170.99   3.199%   $176.46   $176.46   $176.45   $176.50  
  Purchase #3 $177.42   5.681%   $187.4992   $187.50   $187.50   $187.50  
  Purchase #4 $42.31   11.194%   $47.0462   $47.05   $47.05   $47.00  
  Purchase #5 $155.56   8.403%   $168.6317   $168.63   $168.65   $168.60  
  Purchase #6 $236.32   13.587%   $268.4288   $268.43   $268.45   $268.40  
  Purchase #7 $109.60   6.839%   $117.0955   $117.10   $117.10   $117.10  
  7 purchase totals = $957.48       $1,037.1254   $1,037.13   $1,037.15   $1,037.10