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 $141.95   8.716%   $154.3224   $154.32   $154.30   $154.30  
  Purchase #2 $58.29   4.448%   $60.8827   $60.88   $60.90   $60.90  
  Purchase #3 $185.87   6.117%   $197.2397   $197.24   $197.25   $197.20  
  Purchase #4 $243.57   9.783%   $267.3985   $267.40   $267.40   $267.40  
  Purchase #5 $78.58   4.350%   $81.9982   $82.00   $82.00   $82.00  
  Purchase #6 $148.42   10.106%   $163.4193   $163.42   $163.40   $163.40  
  Purchase #7 $239.39   11.448%   $266.7954   $266.80   $266.80   $266.80  
  7 purchase totals = $1,096.07       $1,192.0562   $1,192.06   $1,192.05   $1,192.00