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 $45.91   4.693%   $48.0646   $48.06   $48.05   $48.10  
  Purchase #2 $113.41   8.796%   $123.3855   $123.39   $123.40   $123.40  
  Purchase #3 $159.56   11.333%   $177.6429   $177.64   $177.65   $177.60  
  Purchase #4 $222.44   10.391%   $245.5537   $245.55   $245.55   $245.60  
  Purchase #5 $94.54   3.383%   $97.7383   $97.74   $97.75   $97.70  
  Purchase #6 $134.56   12.725%   $151.6828   $151.68   $151.70   $151.70  
  Purchase #7 $174.65   3.850%   $181.374   $181.37   $181.35   $181.40  
  7 purchase totals = $945.07       $1,025.4418   $1,025.43   $1,025.45   $1,025.50