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 $214.62   9.735%   $235.5133   $235.51   $235.50   $235.50  
  Purchase #2 $161.82   11.741%   $180.8193   $180.82   $180.80   $180.80  
  Purchase #3 $211.39   3.590%   $218.9789   $218.98   $219.00   $219.00  
  Purchase #4 $226.33   4.827%   $237.2549   $237.25   $237.25   $237.30  
  Purchase #5 $22.32   13.480%   $25.3287   $25.33   $25.35   $25.30  
  Purchase #6 $124.68   6.255%   $132.4787   $132.48   $132.50   $132.50  
  Purchase #7 $114.63   6.589%   $122.183   $122.18   $122.20   $122.20  
  7 purchase totals = $1,075.79       $1,152.5568   $1,152.55   $1,152.60   $1,152.60