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 $169.48   13.373%   $192.1446   $192.14   $192.15   $192.10  
  Purchase #2 $239.39   13.177%   $270.9344   $270.93   $270.95   $270.90  
  Purchase #3 $95.84   11.143%   $106.5195   $106.52   $106.50   $106.50  
  Purchase #4 $30.29   5.286%   $31.8911   $31.89   $31.90   $31.90  
  Purchase #5 $71.29   5.729%   $75.3742   $75.37   $75.35   $75.40  
  Purchase #6 $208.75   13.418%   $236.7601   $236.76   $236.75   $236.80  
  Purchase #7 $248.40   5.696%   $262.5489   $262.55   $262.55   $262.50  
  7 purchase totals = $1,063.44       $1,176.1728   $1,176.16   $1,176.15   $1,176.10