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 $42.49   13.141%   $48.0736   $48.07   $48.05   $48.10  
  Purchase #2 $130.94   8.182%   $141.6535   $141.65   $141.65   $141.70  
  Purchase #3 $217.52   8.719%   $236.4856   $236.49   $236.50   $236.50  
  Purchase #4 $124.85   7.851%   $134.652   $134.65   $134.65   $134.70  
  Purchase #5 $85.44   8.117%   $92.3752   $92.38   $92.40   $92.40  
  Purchase #6 $213.55   7.140%   $228.7975   $228.80   $228.80   $228.80  
  Purchase #7 $217.64   12.108%   $243.9919   $243.99   $244.00   $244.00  
  7 purchase totals = $1,032.43       $1,126.0293   $1,126.03   $1,126.05   $1,126.20