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 $168.91   4.750%   $176.9332   $176.93   $176.95   $176.90  
  Purchase #2 $185.96   3.345%   $192.1804   $192.18   $192.20   $192.20  
  Purchase #3 $60.94   5.438%   $64.2539   $64.25   $64.25   $64.30  
  Purchase #4 $163.35   11.359%   $181.9049   $181.90   $181.90   $181.90  
  Purchase #5 $236.66   13.188%   $267.8707   $267.87   $267.85   $267.90  
  Purchase #6 $217.98   5.395%   $229.74   $229.74   $229.75   $229.70  
  Purchase #7 $133.82   5.311%   $140.9272   $140.93   $140.95   $140.90  
  7 purchase totals = $1,167.62       $1,253.8103   $1,253.80   $1,253.85   $1,253.80