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 $199.80   5.234%   $210.2575   $210.26   $210.25   $210.30  
  Purchase #2 $246.60   6.386%   $262.3479   $262.35   $262.35   $262.30  
  Purchase #3 $235.61   5.521%   $248.618   $248.62   $248.60   $248.60  
  Purchase #4 $230.25   9.247%   $251.5412   $251.54   $251.55   $251.50  
  Purchase #5 $216.97   6.183%   $230.3853   $230.39   $230.40   $230.40  
  Purchase #6 $61.92   5.253%   $65.1727   $65.17   $65.15   $65.20  
  Purchase #7 $195.82   9.833%   $215.075   $215.08   $215.10   $215.10  
  7 purchase totals = $1,386.97       $1,483.3976   $1,483.41   $1,483.40   $1,483.40