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 $62.51   11.462%   $69.6749   $69.67   $69.65   $69.70  
  Purchase #2 $227.57   4.716%   $238.3022   $238.30   $238.30   $238.30  
  Purchase #3 $243.79   9.127%   $266.0407   $266.04   $266.05   $266.00  
  Purchase #4 $234.60   13.566%   $266.4258   $266.43   $266.45   $266.40  
  Purchase #5 $137.90   12.127%   $154.6231   $154.62   $154.60   $154.60  
  Purchase #6 $86.38   9.502%   $94.5878   $94.59   $94.60   $94.60  
  Purchase #7 $179.87   7.427%   $193.2289   $193.23   $193.25   $193.20  
  7 purchase totals = $1,172.62       $1,282.8834   $1,282.88   $1,282.90   $1,282.80