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 $78.33   10.394%   $86.4716   $86.47   $86.45   $86.50  
  Purchase #2 $119.96   5.785%   $126.8997   $126.90   $126.90   $126.90  
  Purchase #3 $80.28   8.614%   $87.1953   $87.20   $87.20   $87.20  
  Purchase #4 $106.68   4.153%   $111.1104   $111.11   $111.10   $111.10  
  Purchase #5 $247.43   10.726%   $273.9693   $273.97   $273.95   $274.00  
  Purchase #6 $164.49   6.813%   $175.6967   $175.70   $175.70   $175.70  
  Purchase #7 $170.54   12.714%   $192.2225   $192.22   $192.20   $192.20  
  7 purchase totals = $967.71       $1,053.5655   $1,053.57   $1,053.50   $1,053.60