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 $43.83   13.259%   $49.6414   $49.64   $49.65   $49.60  
  Purchase #2 $245.48   12.491%   $276.1429   $276.14   $276.15   $276.10  
  Purchase #3 $59.75   11.705%   $66.7437   $66.74   $66.75   $66.70  
  Purchase #4 $77.33   9.437%   $84.6276   $84.63   $84.65   $84.60  
  Purchase #5 $243.83   9.529%   $267.0646   $267.06   $267.05   $267.10  
  Purchase #6 $210.45   6.325%   $223.761   $223.76   $223.75   $223.80  
  Purchase #7 $137.81   3.363%   $142.4446   $142.44   $142.45   $142.40  
  7 purchase totals = $1,018.48       $1,110.4258   $1,110.41   $1,110.45   $1,110.30