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 $172.81   8.220%   $187.015   $187.02   $187.00   $187.00  
  Purchase #2 $185.52   11.564%   $206.9735   $206.97   $206.95   $207.00  
  Purchase #3 $217.82   4.501%   $227.6241   $227.62   $227.60   $227.60  
  Purchase #4 $234.64   3.361%   $242.5263   $242.53   $242.55   $242.50  
  Purchase #5 $202.71   11.361%   $225.7399   $225.74   $225.75   $225.70  
  Purchase #6 $217.91   10.210%   $240.1586   $240.16   $240.15   $240.20  
  Purchase #7 $59.87   8.396%   $64.8967   $64.90   $64.90   $64.90  
  7 purchase totals = $1,291.28       $1,394.9341   $1,394.94   $1,394.90   $1,394.90