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 $39.37   13.153%   $44.5483   $44.55   $44.55   $44.50  
  Purchase #2 $214.34   9.677%   $235.0817   $235.08   $235.10   $235.10  
  Purchase #3 $215.90   5.603%   $227.9969   $228.00   $228.00   $228.00  
  Purchase #4 $240.28   5.273%   $252.95   $252.95   $252.95   $253.00  
  Purchase #5 $228.74   6.630%   $243.9055   $243.91   $243.90   $243.90  
  Purchase #6 $46.64   13.155%   $52.7755   $52.78   $52.80   $52.80  
  Purchase #7 $48.59   13.825%   $55.3076   $55.31   $55.30   $55.30  
  7 purchase totals = $1,033.86       $1,112.5655   $1,112.58   $1,112.60   $1,112.60