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 $95.53   11.563%   $106.5761   $106.58   $106.60   $106.60  
  Purchase #2 $92.63   11.869%   $103.6243   $103.62   $103.60   $103.60  
  Purchase #3 $177.57   8.127%   $192.0011   $192.00   $192.00   $192.00  
  Purchase #4 $118.36   6.439%   $125.9812   $125.98   $126.00   $126.00  
  Purchase #5 $146.80   3.424%   $151.8264   $151.83   $151.85   $151.80  
  Purchase #6 $203.50   4.752%   $213.1703   $213.17   $213.15   $213.20  
  Purchase #7 $206.35   9.405%   $225.7572   $225.76   $225.75   $225.80  
  7 purchase totals = $1,040.74       $1,118.9366   $1,118.94   $1,118.95   $1,119.00