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 $69.72   9.478%   $76.3281   $76.33   $76.35   $76.30  
  Purchase #2 $214.95   5.863%   $227.5525   $227.55   $227.55   $227.60  
  Purchase #3 $205.42   3.458%   $212.5234   $212.52   $212.50   $212.50  
  Purchase #4 $48.91   8.233%   $52.9368   $52.94   $52.95   $52.90  
  Purchase #5 $62.45   3.554%   $64.6695   $64.67   $64.65   $64.70  
  Purchase #6 $243.34   4.195%   $253.5481   $253.55   $253.55   $253.50  
  Purchase #7 $55.50   6.854%   $59.304   $59.30   $59.30   $59.30  
  7 purchase totals = $900.29       $946.8624   $946.86   $946.85   $946.80