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 $13.98   4.660%   $14.6315   $14.63   $14.65   $14.60  
  Purchase #2 $249.67   3.304%   $257.9191   $257.92   $257.90   $257.90  
  Purchase #3 $239.31   4.636%   $250.4044   $250.40   $250.40   $250.40  
  Purchase #4 $110.36   7.396%   $118.5222   $118.52   $118.50   $118.50  
  Purchase #5 $218.63   12.798%   $246.6103   $246.61   $246.60   $246.60  
  Purchase #6 $98.32   3.824%   $102.0798   $102.08   $102.10   $102.10  
  Purchase #7 $39.71   6.267%   $42.1986   $42.20   $42.20   $42.20  
  7 purchase totals = $969.98       $1,032.3659   $1,032.36   $1,032.35   $1,032.30