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 $124.68   13.176%   $141.1078   $141.11   $141.10   $141.10  
  Purchase #2 $154.37   12.262%   $173.2988   $173.30   $173.30   $173.30  
  Purchase #3 $222.48   8.621%   $241.66   $241.66   $241.65   $241.70  
  Purchase #4 $183.44   4.200%   $191.1445   $191.14   $191.15   $191.10  
  Purchase #5 $216.91   6.117%   $230.1784   $230.18   $230.20   $230.20  
  Purchase #6 $147.42   4.433%   $153.9551   $153.96   $153.95   $154.00  
  Purchase #7 $136.69   3.868%   $141.9772   $141.98   $142.00   $142.00  
  7 purchase totals = $1,185.99       $1,273.3218   $1,273.33   $1,273.35   $1,273.40