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 $213.63   11.210%   $237.5779   $237.58   $237.60   $237.60  
  Purchase #2 $229.80   10.680%   $254.3426   $254.34   $254.35   $254.30  
  Purchase #3 $79.72   6.680%   $85.0453   $85.05   $85.05   $85.00  
  Purchase #4 $238.75   4.391%   $249.2335   $249.23   $249.25   $249.20  
  Purchase #5 $144.25   13.702%   $164.0151   $164.02   $164.00   $164.00  
  Purchase #6 $162.43   8.454%   $176.1618   $176.16   $176.15   $176.20  
  Purchase #7 $82.94   6.729%   $88.521   $88.52   $88.50   $88.50  
  7 purchase totals = $1,151.52       $1,254.8972   $1,254.90   $1,254.90   $1,254.80