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 $148.86   3.699%   $154.3663   $154.37   $154.35   $154.40  
  Purchase #2 $188.42   5.187%   $198.1933   $198.19   $198.20   $198.20  
  Purchase #3 $192.90   6.703%   $205.8301   $205.83   $205.85   $205.80  
  Purchase #4 $156.93   3.745%   $162.807   $162.81   $162.80   $162.80  
  Purchase #5 $167.93   7.742%   $180.9311   $180.93   $180.95   $180.90  
  Purchase #6 $243.42   3.291%   $251.431   $251.43   $251.45   $251.40  
  Purchase #7 $72.65   9.657%   $79.6658   $79.67   $79.65   $79.70  
  7 purchase totals = $1,171.11       $1,233.2246   $1,233.23   $1,233.25   $1,233.20