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 $162.42   8.771%   $176.6659   $176.67   $176.65   $176.70  
  Purchase #2 $247.93   9.380%   $271.1858   $271.19   $271.20   $271.20  
  Purchase #3 $151.82   8.125%   $164.1554   $164.16   $164.15   $164.20  
  Purchase #4 $211.26   6.339%   $224.6518   $224.65   $224.65   $224.70  
  Purchase #5 $230.30   6.787%   $245.9305   $245.93   $245.95   $245.90  
  Purchase #6 $221.76   10.702%   $245.4928   $245.49   $245.50   $245.50  
  Purchase #7 $96.78   9.797%   $106.2615   $106.26   $106.25   $106.30  
  7 purchase totals = $1,322.27       $1,434.3437   $1,434.35   $1,434.35   $1,434.50