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 $65.50   11.618%   $73.1098   $73.11   $73.10   $73.10  
  Purchase #2 $197.84   8.668%   $214.9888   $214.99   $215.00   $215.00  
  Purchase #3 $127.79   13.792%   $145.4148   $145.41   $145.40   $145.40  
  Purchase #4 $220.98   12.785%   $249.2323   $249.23   $249.25   $249.20  
  Purchase #5 $117.47   13.755%   $133.628   $133.63   $133.65   $133.60  
  Purchase #6 $101.56   13.335%   $115.103   $115.10   $115.10   $115.10  
  Purchase #7 $236.82   3.260%   $244.5403   $244.54   $244.55   $244.50  
  7 purchase totals = $1,067.96       $1,176.0170   $1,176.01   $1,176.05   $1,175.90