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 $208.27   13.417%   $236.2136   $236.21   $236.20   $236.20  
  Purchase #2 $208.93   5.607%   $220.6447   $220.64   $220.65   $220.60  
  Purchase #3 $115.42   13.528%   $131.034   $131.03   $131.05   $131.00  
  Purchase #4 $218.81   10.375%   $241.5115   $241.51   $241.50   $241.50  
  Purchase #5 $228.94   8.141%   $247.578   $247.58   $247.60   $247.60  
  Purchase #6 $228.53   11.780%   $255.4508   $255.45   $255.45   $255.50  
  Purchase #7 $160.32   5.537%   $169.1969   $169.20   $169.20   $169.20  
  7 purchase totals = $1,369.22       $1,501.6295   $1,501.62   $1,501.65   $1,501.60