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 $58.93   4.563%   $61.619   $61.62   $61.60   $61.60  
  Purchase #2 $201.46   8.763%   $219.1139   $219.11   $219.10   $219.10  
  Purchase #3 $218.46   13.372%   $247.6725   $247.67   $247.65   $247.70  
  Purchase #4 $132.64   7.286%   $142.3042   $142.30   $142.30   $142.30  
  Purchase #5 $199.70   6.554%   $212.7883   $212.79   $212.80   $212.80  
  Purchase #6 $225.50   9.641%   $247.2405   $247.24   $247.25   $247.20  
  Purchase #7 $118.83   6.541%   $126.6027   $126.60   $126.60   $126.60  
  7 purchase totals = $1,155.52       $1,257.3411   $1,257.33   $1,257.30   $1,257.30