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 $216.95   4.286%   $226.2485   $226.25   $226.25   $226.20  
  Purchase #2 $225.63   10.153%   $248.5382   $248.54   $248.55   $248.50  
  Purchase #3 $199.97   6.226%   $212.4201   $212.42   $212.40   $212.40  
  Purchase #4 $22.87   9.204%   $24.975   $24.98   $25.00   $25.00  
  Purchase #5 $174.77   5.780%   $184.8717   $184.87   $184.85   $184.90  
  Purchase #6 $54.57   12.785%   $61.5468   $61.55   $61.55   $61.50  
  Purchase #7 $168.86   9.253%   $184.4846   $184.48   $184.50   $184.50  
  7 purchase totals = $1,063.62       $1,143.0849   $1,143.09   $1,143.10   $1,143.00