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 $219.42   10.152%   $241.6955   $241.70   $241.70   $241.70  
  Purchase #2 $181.96   7.365%   $195.3614   $195.36   $195.35   $195.40  
  Purchase #3 $29.65   8.509%   $32.1729   $32.17   $32.15   $32.20  
  Purchase #4 $238.53   3.174%   $246.1009   $246.10   $246.10   $246.10  
  Purchase #5 $185.51   12.577%   $208.8416   $208.84   $208.85   $208.80  
  Purchase #6 $183.93   5.322%   $193.7188   $193.72   $193.70   $193.70  
  Purchase #7 $76.73   7.666%   $82.6121   $82.61   $82.60   $82.60  
  7 purchase totals = $1,115.73       $1,200.5032   $1,200.50   $1,200.45   $1,200.50