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 $195.52   9.471%   $214.0377   $214.04   $214.05   $214.00  
  Purchase #2 $185.87   10.604%   $205.5797   $205.58   $205.60   $205.60  
  Purchase #3 $79.59   3.282%   $82.2021   $82.20   $82.20   $82.20  
  Purchase #4 $110.81   9.409%   $121.2361   $121.24   $121.25   $121.20  
  Purchase #5 $95.41   8.566%   $103.5828   $103.58   $103.60   $103.60  
  Purchase #6 $196.63   4.494%   $205.4666   $205.47   $205.45   $205.50  
  Purchase #7 $244.30   3.405%   $252.6184   $252.62   $252.60   $252.60  
  7 purchase totals = $1,108.13       $1,184.7234   $1,184.73   $1,184.75   $1,184.70