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 $167.76   5.170%   $176.4332   $176.43   $176.45   $176.40  
  Purchase #2 $214.26   10.812%   $237.4258   $237.43   $237.45   $237.40  
  Purchase #3 $15.79   7.478%   $16.9708   $16.97   $16.95   $17.00  
  Purchase #4 $197.69   6.724%   $210.9827   $210.98   $211.00   $211.00  
  Purchase #5 $124.51   3.268%   $128.579   $128.58   $128.60   $128.60  
  Purchase #6 $195.87   8.307%   $212.1409   $212.14   $212.15   $212.10  
  Purchase #7 $199.33   7.564%   $214.4073   $214.41   $214.40   $214.40  
  7 purchase totals = $1,115.21       $1,196.9397   $1,196.94   $1,197.00   $1,196.90