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 $32.95   6.404%   $35.0601   $35.06   $35.05   $35.10  
  Purchase #2 $163.29   6.662%   $174.1684   $174.17   $174.15   $174.20  
  Purchase #3 $204.88   6.166%   $217.5129   $217.51   $217.50   $217.50  
  Purchase #4 $119.53   13.599%   $135.7849   $135.78   $135.80   $135.80  
  Purchase #5 $119.77   12.758%   $135.0503   $135.05   $135.05   $135.10  
  Purchase #6 $217.40   13.462%   $246.6664   $246.67   $246.65   $246.70  
  Purchase #7 $112.63   6.610%   $120.0748   $120.07   $120.05   $120.10  
  7 purchase totals = $970.45       $1,064.3178   $1,064.31   $1,064.25   $1,064.50