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 $146.63   3.671%   $152.0128   $152.01   $152.00   $152.00  
  Purchase #2 $236.59   5.366%   $249.2854   $249.29   $249.30   $249.30  
  Purchase #3 $73.38   12.386%   $82.4688   $82.47   $82.45   $82.50  
  Purchase #4 $233.68   13.565%   $265.3787   $265.38   $265.40   $265.40  
  Purchase #5 $164.70   8.575%   $178.823   $178.82   $178.80   $178.80  
  Purchase #6 $166.92   11.734%   $186.5064   $186.51   $186.50   $186.50  
  Purchase #7 $74.44   4.301%   $77.6417   $77.64   $77.65   $77.60  
  7 purchase totals = $1,096.34       $1,192.1168   $1,192.12   $1,192.10   $1,192.10