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 $184.81   5.287%   $194.5809   $194.58   $194.60   $194.60  
  Purchase #2 $233.35   8.315%   $252.7531   $252.75   $252.75   $252.80  
  Purchase #3 $57.47   6.716%   $61.3297   $61.33   $61.35   $61.30  
  Purchase #4 $86.77   8.834%   $94.4353   $94.44   $94.45   $94.40  
  Purchase #5 $19.58   13.751%   $22.2724   $22.27   $22.25   $22.30  
  Purchase #6 $173.71   6.500%   $185.0012   $185.00   $185.00   $185.00  
  Purchase #7 $122.65   8.131%   $132.6227   $132.62   $132.60   $132.60  
  7 purchase totals = $878.34       $942.9953   $942.99   $943.00   $943.00