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 $197.40   13.405%   $223.8615   $223.86   $223.85   $223.90  
  Purchase #2 $206.93   3.472%   $214.1146   $214.11   $214.10   $214.10  
  Purchase #3 $148.40   3.450%   $153.5198   $153.52   $153.50   $153.50  
  Purchase #4 $64.79   7.206%   $69.4588   $69.46   $69.45   $69.50  
  Purchase #5 $144.57   12.284%   $162.329   $162.33   $162.35   $162.30  
  Purchase #6 $245.25   6.608%   $261.4561   $261.46   $261.45   $261.50  
  Purchase #7 $240.57   8.755%   $261.6319   $261.63   $261.65   $261.60  
  7 purchase totals = $1,247.91       $1,346.3717   $1,346.37   $1,346.35   $1,346.40