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 $62.85   7.794%   $67.7485   $67.75   $67.75   $67.70  
  Purchase #2 $192.90   6.807%   $206.0307   $206.03   $206.05   $206.00  
  Purchase #3 $195.80   8.635%   $212.7073   $212.71   $212.70   $212.70  
  Purchase #4 $176.69   12.555%   $198.8734   $198.87   $198.85   $198.90  
  Purchase #5 $194.78   3.826%   $202.2323   $202.23   $202.25   $202.20  
  Purchase #6 $29.99   12.449%   $33.7235   $33.72   $33.70   $33.70  
  Purchase #7 $152.78   12.292%   $171.5597   $171.56   $171.55   $171.60  
  7 purchase totals = $1,005.79       $1,092.8754   $1,092.87   $1,092.85   $1,092.80