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 $71.81   5.317%   $75.6281   $75.63   $75.65   $75.60  
  Purchase #2 $219.25   8.682%   $238.2853   $238.29   $238.30   $238.30  
  Purchase #3 $115.92   11.482%   $129.2299   $129.23   $129.25   $129.20  
  Purchase #4 $164.52   9.442%   $180.054   $180.05   $180.05   $180.10  
  Purchase #5 $112.79   4.832%   $118.24   $118.24   $118.25   $118.20  
  Purchase #6 $168.59   13.365%   $191.1221   $191.12   $191.10   $191.10  
  Purchase #7 $102.49   6.698%   $109.3548   $109.35   $109.35   $109.40  
  7 purchase totals = $955.37       $1,041.9142   $1,041.91   $1,041.95   $1,041.90