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 $141.77   7.728%   $152.726   $152.73   $152.75   $152.70  
  Purchase #2 $192.59   7.441%   $206.9206   $206.92   $206.90   $206.90  
  Purchase #3 $145.61   10.859%   $161.4218   $161.42   $161.40   $161.40  
  Purchase #4 $82.77   9.582%   $90.701   $90.70   $90.70   $90.70  
  Purchase #5 $190.43   3.751%   $197.573   $197.57   $197.55   $197.60  
  Purchase #6 $134.29   11.543%   $149.7911   $149.79   $149.80   $149.80  
  Purchase #7 $105.68   8.785%   $114.964   $114.96   $114.95   $115.00  
  7 purchase totals = $993.14       $1,074.0975   $1,074.09   $1,074.05   $1,074.10