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 $162.85   13.325%   $184.5498   $184.55   $184.55   $184.50  
  Purchase #2 $165.41   6.527%   $176.2063   $176.21   $176.20   $176.20  
  Purchase #3 $213.79   7.238%   $229.2641   $229.26   $229.25   $229.30  
  Purchase #4 $111.60   5.158%   $117.3563   $117.36   $117.35   $117.40  
  Purchase #5 $93.43   5.217%   $98.3042   $98.30   $98.30   $98.30  
  Purchase #6 $246.33   9.525%   $269.7929   $269.79   $269.80   $269.80  
  Purchase #7 $83.64   7.857%   $90.2116   $90.21   $90.20   $90.20  
  7 purchase totals = $1,077.05       $1,165.6852   $1,165.68   $1,165.65   $1,165.70