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 $134.73   5.841%   $142.5996   $142.60   $142.60   $142.60  
  Purchase #2 $183.65   11.728%   $205.1885   $205.19   $205.20   $205.20  
  Purchase #3 $63.95   6.212%   $67.9226   $67.92   $67.90   $67.90  
  Purchase #4 $169.51   4.696%   $177.4702   $177.47   $177.45   $177.50  
  Purchase #5 $57.83   9.516%   $63.3331   $63.33   $63.35   $63.30  
  Purchase #6 $78.41   11.169%   $87.1676   $87.17   $87.15   $87.20  
  Purchase #7 $11.65   10.410%   $12.8628   $12.86   $12.85   $12.90  
  7 purchase totals = $699.73       $756.5444   $756.54   $756.50   $756.60