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 $191.77   7.751%   $206.6341   $206.63   $206.65   $206.60  
  Purchase #2 $210.64   5.694%   $222.6338   $222.63   $222.65   $222.60  
  Purchase #3 $118.33   5.274%   $124.5707   $124.57   $124.55   $124.60  
  Purchase #4 $70.53   8.822%   $76.7522   $76.75   $76.75   $76.80  
  Purchase #5 $89.26   13.114%   $100.9656   $100.97   $100.95   $101.00  
  Purchase #6 $90.89   6.131%   $96.4625   $96.46   $96.45   $96.50  
  Purchase #7 $191.33   5.342%   $201.5508   $201.55   $201.55   $201.60  
  7 purchase totals = $962.75       $1,029.5697   $1,029.56   $1,029.55   $1,029.70