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 $214.44   10.453%   $236.8554   $236.86   $236.85   $236.90  
  Purchase #2 $64.73   5.526%   $68.307   $68.31   $68.30   $68.30  
  Purchase #3 $156.62   7.597%   $168.5184   $168.52   $168.50   $168.50  
  Purchase #4 $96.42   12.236%   $108.218   $108.22   $108.20   $108.20  
  Purchase #5 $179.38   7.240%   $192.3671   $192.37   $192.35   $192.40  
  Purchase #6 $113.93   11.388%   $126.9043   $126.90   $126.90   $126.90  
  Purchase #7 $241.69   7.356%   $259.4687   $259.47   $259.45   $259.50  
  7 purchase totals = $1,067.21       $1,160.6389   $1,160.65   $1,160.55   $1,160.70