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 $68.34   11.767%   $76.3816   $76.38   $76.40   $76.40  
  Purchase #2 $211.33   11.348%   $235.3117   $235.31   $235.30   $235.30  
  Purchase #3 $209.28   12.491%   $235.4212   $235.42   $235.40   $235.40  
  Purchase #4 $149.69   7.428%   $160.809   $160.81   $160.80   $160.80  
  Purchase #5 $141.45   13.567%   $160.6405   $160.64   $160.65   $160.60  
  Purchase #6 $248.50   8.253%   $269.0087   $269.01   $269.00   $269.00  
  Purchase #7 $22.38   10.120%   $24.6449   $24.64   $24.65   $24.60  
  7 purchase totals = $1,050.97       $1,162.2176   $1,162.21   $1,162.20   $1,162.10