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 $63.27   8.484%   $68.6378   $68.64   $68.65   $68.60  
  Purchase #2 $236.82   4.162%   $246.6764   $246.68   $246.70   $246.70  
  Purchase #3 $217.30   8.356%   $235.4576   $235.46   $235.45   $235.50  
  Purchase #4 $155.34   3.781%   $161.2134   $161.21   $161.20   $161.20  
  Purchase #5 $139.29   6.344%   $148.1266   $148.13   $148.15   $148.10  
  Purchase #6 $122.54   4.867%   $128.504   $128.50   $128.50   $128.50  
  Purchase #7 $57.71   6.278%   $61.333   $61.33   $61.35   $61.30  
  7 purchase totals = $992.27       $1,049.9488   $1,049.95   $1,050.00   $1,049.90