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 $59.75   4.119%   $62.2111   $62.21   $62.20   $62.20  
  Purchase #2 $215.45   8.284%   $233.2979   $233.30   $233.30   $233.30  
  Purchase #3 $105.58   4.540%   $110.3733   $110.37   $110.35   $110.40  
  Purchase #4 $176.62   11.424%   $196.7971   $196.80   $196.80   $196.80  
  Purchase #5 $60.89   7.182%   $65.2631   $65.26   $65.25   $65.30  
  Purchase #6 $148.40   6.190%   $157.586   $157.59   $157.60   $157.60  
  Purchase #7 $106.37   8.383%   $115.287   $115.29   $115.30   $115.30  
  7 purchase totals = $873.06       $940.8155   $940.82   $940.80   $940.90