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 $44.76   3.764%   $46.4448   $46.44   $46.45   $46.40  
  Purchase #2 $98.25   3.229%   $101.4225   $101.42   $101.40   $101.40  
  Purchase #3 $169.31   7.817%   $182.545   $182.55   $182.55   $182.50  
  Purchase #4 $216.95   4.400%   $226.4958   $226.50   $226.50   $226.50  
  Purchase #5 $90.44   5.553%   $95.4621   $95.46   $95.45   $95.50  
  Purchase #6 $192.34   6.475%   $204.794   $204.79   $204.80   $204.80  
  Purchase #7 $189.45   9.335%   $207.1352   $207.14   $207.15   $207.10  
  7 purchase totals = $1,001.50       $1,064.2994   $1,064.30   $1,064.30   $1,064.20