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 $174.87   11.860%   $195.6096   $195.61   $195.60   $195.60  
  Purchase #2 $189.44   11.314%   $210.8732   $210.87   $210.85   $210.90  
  Purchase #3 $240.86   10.670%   $266.5598   $266.56   $266.55   $266.60  
  Purchase #4 $69.27   4.539%   $72.4142   $72.41   $72.40   $72.40  
  Purchase #5 $224.64   11.485%   $250.4399   $250.44   $250.45   $250.40  
  Purchase #6 $153.96   8.780%   $167.4777   $167.48   $167.50   $167.50  
  Purchase #7 $102.37   10.695%   $113.3185   $113.32   $113.30   $113.30  
  7 purchase totals = $1,155.41       $1,276.6929   $1,276.69   $1,276.65   $1,276.70