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 $77.95   10.841%   $86.4006   $86.40   $86.40   $86.40  
  Purchase #2 $209.33   9.492%   $229.1996   $229.20   $229.20   $229.20  
  Purchase #3 $147.37   5.781%   $155.8895   $155.89   $155.90   $155.90  
  Purchase #4 $99.45   6.506%   $105.9202   $105.92   $105.90   $105.90  
  Purchase #5 $44.47   5.615%   $46.967   $46.97   $46.95   $47.00  
  Purchase #6 $234.25   4.803%   $245.501   $245.50   $245.50   $245.50  
  Purchase #7 $236.65   5.240%   $249.0505   $249.05   $249.05   $249.10  
  7 purchase totals = $1,049.47       $1,118.9284   $1,118.93   $1,118.90   $1,119.00