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 $206.80   12.797%   $233.2642   $233.26   $233.25   $233.30  
  Purchase #2 $103.41   9.563%   $113.2991   $113.30   $113.30   $113.30  
  Purchase #3 $156.31   8.854%   $170.1497   $170.15   $170.15   $170.10  
  Purchase #4 $62.91   12.804%   $70.965   $70.97   $70.95   $71.00  
  Purchase #5 $185.53   4.306%   $193.5189   $193.52   $193.50   $193.50  
  Purchase #6 $223.56   8.509%   $242.5827   $242.58   $242.60   $242.60  
  Purchase #7 $136.52   11.810%   $152.643   $152.64   $152.65   $152.60  
  7 purchase totals = $1,075.04       $1,176.4226   $1,176.42   $1,176.40   $1,176.40